The experiments here described make provision for some of the eventualities not covered by the previous experiments of Taylor and Purchase, and appear to give a more definite answer to the question on the effect of the presence of parasitic worms in aiding the entry of bacteria into the body.

Although the conditions, in these experiments, appear to have been very favourable for the bacteria present in the lumen of the bowel to invade the host through abrasions of the wall caused by the parasitic worms, the evidence of assistance given by the worms to the entry of bacteria has not been obtained. In view of these findings, and taking into consideration other experimental results, it seems highly probable that the injuries caused to the bowel wall by parasitic worms in general do not play any important part in bringing about bacterial infection from the lumen of the intestine.

In 1931 Dr M. V. Lebour drew my attention to a larval Trematode (one of the “Hugetailed Monostome” group of H. M. Miller, 1925) which occurred quite frequently in Turritella communis from the Rame Mud, Plymouth. During 1932–4 I examined 541 Turritella communis from the same locality and an 8 per cent. general infection with four species of closely related cercariae was recorded, but the species which was common the previous year did not occur once. 180 Turritella communis from Naples revealed a 5 per cent, infection of two other closely related species.

Cercaria Ephemera Lebour belongs to the group of Monostome cercariae which have been proved to belong to the Notocotylidae. This species probably belongs to the genus Notocotylus.

This is the first report of Taenia tenuicollis Rudolphi, 1819, and its larva, Cysticercus talpae Rudolphi, 1819, from North America. In the process of identification of the specimens described below, it became evident that no adequate figures of this species had been published, that this specific name had been given by recent authors to more than one species of Cestode, and that several characters of value in specific differentiation had not been described. The description given here is based entirely upon specimens from Mustela vison collected by Dr R. G. Law of the Experimental Fur Farm, Kirkfield, Ontario. Details published by Thienemann (1906) and others on the European specimens of this species are given in the accompanying comparative table.

1. The second ecdyses experimentally produced in 1 in 20 and other watery dilutions of Milton hypochlorite are described. These occur without the detachment of a typical cap. The larva is passively propelled part of the way out through a hole at the anterior tip of the sheath, and completes its emergence by its own movements.

The explanation of this is that the chlorine in the Milton solution alters the chemical composition of the sheath with two results: (a) the permeability of the sheath is altered so that increased internal pressure results, by which the larva is propelled out of the hole at the anterior tip, and (b) the sheath is rendered soluble in the NaOH in the Milton solution so that it is subsequently dissolved. The larva is expelled through a hole at the anterior tip before the whole sheath is dissolved because the sheath gives way here first to the combined effects of the increased internal pressure and the solvent action of the NaOH, this being its weakest point, where the remains of the mouth of the second larva are.

The larva is only rarely propelled completely out by the raised internal pressure, namely, when the hole at the anterior tip is big enough to allow its widest part, at the base of its oesophageal region, to pass; or, alternatively, when the internal pressure is high enough to force this part of it through the hole. Usually it requires the help of its own movements to force this widest part of it through the hole.

2. Neither chlorine, oxygen, nor caustic soda alone can cause ecdyses, although the latter may dissolve the sheaths of larvae kept long in cultures or exposed long upon pastures, so that a chemical change in their sheaths has occurred similar to that just described. Caustic soda may then also so weaken and thin the sheaths that larvae, if they are active enough, may break their way out.

Neither carbonic nor hydrochloric acids, nor solutions of sodium chloride, could alone cause ecdyses; nor could solutions of sodium carbonate, although these acted upon “older” larvae in much the same way as solutions of caustic soda, which they must contain.

3. Larvae, however, whether they were recently mature or had been long kept in cultures, showed, when they were treated with chlorine water or with hypochlorite solutions acidified with excess of either HCl or acetic acids, effects which indicated that the conclusion described in (a) above was correct. They never exsheathed, but their sheaths were blistered and thinned and frequently distended also, with the exception of the cap which is detached at the ecdysis; this was usually neither blistered, thinned nor distended. This distension was especially marked when these larvae were transferred, after this treatment with chlorine, to solutions hypotonic to them. In hypertonic solutions, on the other hand, the larvae were shrunken. This perhaps explains why larvae are often shrunken away from their sheaths in old cultures from which much evaporation has occurred or when they have been exposed upon pastures.

Their sheaths were, moreover, rendered soluble in 0·4 or 0·8 per cent. NaOH by this treatment with chlorine, so that treatment with chlorine, followed by immersion in weak NaOH, will exsheath the larvae, whether they are active or not, by dissolving off their sheaths. This probably explains why larvae exposed on pastures or kept long in cultures, exsheath sometimes in alkaline media such as artificial pancreatic juice, or in the saliva of sheep.

4. Observation of ecdyses that occurred at 38° C. in about 8 days in mixtures of 0·5 per cent. solutions of HCl and 0·5 per cent. NaOH or in 0·5 per cent. HCl followed by 0·5 or 0·8 per cent. NaOH, showed that these always occurred by the detachment of a typical cap, and that the process was essentially the same as that described above. An alteration of the permeability of the sheath occurred by which the pressure inside it was increased, so that the sheath was often distended. The sheath was at the same time rendered soluble in NaOH.

The cap which was detached at the ecdysis resisted, however, this distension, perhaps because it had a slightly different chemical composition, so that tension existed at the base of this more rigid cap, between it and the more flexible and elastic part of the sheath behind it. The tension at this point was further observed to be increased by specific rotatory movements of the oral end of the larva, which incidentally also determined the length of the cap, and by movements of the more flexible and elastic part of the sheath behind the cap, by which it could be repeatedly rolled up on to the cap and back again, as rubber tubing may be rolled up on to a tap. All these movements, especially when they acted upon a distended sheath, ruptured first the inner layer of the sheath at the base of the cap, and then the much stronger outer layer.

The larva then emerged by its own movements; or sometimes it was propelled out passively part of the way by the release of the high internal pressure.

Both the rotatory movements of the oral end of the larva before the detachment of the cap, and the bending and swimming movements of the whole larva by which it extricates itself from the sheath after the cap has been detached, are essential to successful and normal ecdyses. The rotatory movements of the oral end are probably most effective when the oral tip of the sheath is fixed against some resistant object, as skin-penetrating larvae may, for example, fix it against the skin. This fixation of the oral end is not, however, necessary, because most of the ecdyses here recorded occurred in this way in drops quite free of any solid or semi-solid matter.

5. Some experiments are briefly described which indicate that mechanical damage to the sheaths, or friction applied to them, cannot be more than secondary factors which influence only the ecdyses of so-called “older” larvae, whose sheaths are already chemically altered by climatic factors or long life in cultures, with results similar to those which follow treatment with chlorine.

6. It is suggested that factors similar to those indicated above may be present in the stomach and duodenum of the host and may govern any second ecdyses that occur in these situations; and that changes in the sheaths, similar to those produced by chlorine in the experiments here described, may be produced outside the body of the host, by climatic factors, so that the sheaths become soluble in the saliva or other alkaline digestive juices.

7. All attempts failed to induce the third ecdysis of larvae exsheathed and sterilised by 1 in 20 dilutions of Milton with water, and kept in sterile media until they were ready for this ecdysis. These larvae also, like the infective larvae, were susceptible to changes in the tonicity of the media in which they were kept, so that their sheaths could be alternately distended or collapsed upon them, and the larvae themselves could be shrunken or restored to normal by alterations in the concentration of the media. These third (or first parasitic) larvae showed a remarkable power of resistance to such treatment and seemed to be more resistant to it than infective larvae are.

8. Further investigations of the second ecdyses by biophysical methods may bring all the ecdyses of parasitic nematodes under experimental control and so make possible the artificial cultivation of the adult parasites. They may also suggest methods of altering the permeability of the cuticle of adult nematodes, so that anthelmintics may be found which will penetrate this more readily and at the same time will not be toxic to the host.

A second species of the genus Endorchis is described—E. mandubé; also new species of the rare genera Monticellia, Amphoteromorphus and Nomimoscolex, viz. Monticellia piracatinga, M. rugosa, Amphoteromorphus parkarmoo, Nomimoscolex piracatinga and N. kaparari.

A new genus Manaosia is created to contain the anomalous species M. braço de moça. Proteocephalus lenha becomes Nomimoscolex lenha.

The species Spatulifer surubim, originally described by me as Peltidocotyle rugosa and later referred to the Amphilaphorchidinae, is now regarded as a species of the Monticelliinae.

The eight known species of the Monticelliinae are all referred to the single genus Monticellia, since, differences in vitellaria distribution not corresponding to differences of scolex form, the only alternative is to create an unnecessary number of genera. The genera Goezeella Fuhrmann and Spatulifer Woodland are thus regarded as superfluous.

“Ephedrocephalus” lobosus is removed from the Ephedrocephalinae (which retains its single species E. microcephalus) and, with the two species of “Amphilaphorchis” recently described by me, is placed in Fuhrmann's genus Rudolphiella, now re-established, in the subfamily Rudolphiellinae, thus replacing the Amphilaphorchidinae.

The complete list of known subfamilies, genera and species of the Proteocephalidae described from the Amazon, amended in accordance with the above conclusions, has been published in my last paper on the subject (Woodland, 1935).

Large populations of the new species of Entodinium were found in 27 out of 120 stomachs (from the paunch to reticulum) of Bos taurus from various regions of Yugoslavia. The stomach content was fixed in 4 per cent. formaldehyde. Unstained glycerine mounts and material stained in iron haematoxylin and Mallory's phosphor-molybden haematoxylin were used. Twenty individuals from each population, i.e. 540 individuals in all, were measured. The length was found to vary from 26·25 to 38·5μ, and the width from 24·5 to 31·5μ. The relation between the length and the width was 1·16, which indicates the average degree of rotundity. This rotundity, especially noticeable in individuals in which the adoral membranelle zone is retracted, may sometimes be less pronounced at the anterior end. Entodinium bovis is considerably flattened, so that its thickness does not exceed 6–10μ. The pharynx is curved dorsally. The cuticle is longitudinally striated. The ectoplasm is more developed in the anal region than laterally. The macronucleus is elongated, 10·5–21 × 3·5–5×25μ, and is thicker at its anterior end. The micronucleus is round and lies ventral to the macronucleus at a point about the middle of its length. The contractile vacuole lies ventral to the macronucleus, near to its anterior end. The anus is usually situated in the middle of the posterior end of the ciliate, though sometimes it lies slightly ventral.

An account is given of an apparently undescribed virus disease. The virus appears spontaneously in the glasshouse affecting tobacco seedlings in the seed boxes. The symptoms on a number of hosts are described. The chief characteristic of the virus is its failure to become systemic in any host plant so far tested. It is, however, occasionally found in the roots of young tobacco plants, usually in the case of those naturally infected. Certain physical properties of the virus have been investigated. Its dilution end-point appears to be about 1:10,000; its longevity in extracted sap is about 20 days, the thermal death-point is 72° C. The virus shows a strong resistance to alcohol, remaining viable in 99 per cent, alcohol for 71 hours so far as tested.

It is not known how the virus is transmitted in nature, and no insect vector has as yet been identified.

The virus has been transmitted to healthy cowpeas by spraying them with a suspension of the virus by means of an atomiser.

By the Elford method of ultra-filtration the particle size is found to be 20–30μμ.

The virus is compared with that of the American tobacco ringspot, and methods of differentiating the two are indicated.

1. “Trichomonas” keilini n.sp. has three anterior flagella, and a short undulating membrane, whose bordering flagellum does not become free. The flagella arise from an anterior blepharoplast. There is a single nucleus, anteriorly placed, and a mouth, but no basal fibre to the undulating membrane. An axostyle may be present or absent, but when present it is siderophilic. The method of multiplication of “T.” keilini is similar to that of T. hominis and T. batrachorum.

2. “T.” keilini was found in water from a pond in Lincolnshire.

3. It has been cultivated in serum-saline media, in hay infusion, and in pond or rain water with boiled wheat grains, from 4 to 31° C.

4. Cysts have never been found.

I should like to record my gratitude to Prof. Keilin, F.R.S., who gave me the sample of water in which I first saw the organism, and who gave me encouragement throughout this study; and to Mr Clifford Dobell, F.R.S., for the gift of the macaque-human strain of Trichomonas and for so kindly reading through and criticising this manuscript.

1. Perispiracular glands are present in the larvae of Anopheles and Culex.

2. These glands secrete an oily substance which is responsible for the hydrofuge properties of the spiracular region of mosquito larvae.

3. The differential wetting of the spiracular region and the action of oil on mosquito larvae depend on the presence of this oily secretion.

There are conspicuous differences in respect of hibernation among the mosquitoes; for certain species, such as Culex pipiens and Anopheles maculipennis, hibernate as adults, but others, for instance A. claviger (bifurcates), pass the winter as larvae. These differences have been the subject of many investigations and of much theoretical discussion; perusal of the literature suggests that we still lack a sufficient knowledge of the facts. It is known that an accumulation of fat in autumn is characteristic of those mosquitoes which hibernate as adults, as it is of several insects of other orders. But it seems that little is known of the quantity of fat stored, or of the rate at which it disappears as winter passes. It is my present purpose to set out certain observations on the composition of adult female Culex pipiens at different times during the period of hibernation. Later it may be possible to make an experimental study of the causes of hibernation and to discuss the relevant literature. But at the moment let it suffice to refer to the following papers, from which the reader may inform himself of the present state of knowledge and theory: de Boissezon (1930), Roubaud (1932), and Shlenova (1933). The paper by Hecht (1933) contains a valuable summary of the subject.

Habitat and Material. Seven specimens taken on the gills of Serranus cabrilla at Plymouth on 11. v. 1934 and kindly presented to me by Dr R. Gurney.

Since the publication of the original paper by Sowerby (1806) no investigator appears to have thoroughly examined Lernaeenicus spratta; even Scott and Scott (1913) in their monograph do not figure all the appendages.

In this paper an account is given of new forms discovered by the writer during a survey of the parasites of mussels and cockles, obtained chiefly from the estuary at Conway, but also from other beds on the North Wales coast. The trematode parasites of shellfish in this area have not previously been dealt with, although several forms have been described from the Liverpool Bay area by the late Prof. Johnstone and his colleagues. Few additions have been made to our knowledge of the early stages of British marine Trematodes since the publication of a series of papers by Lebour (1912) and Nicoll (1914).

A new genus is here described for the reception of three species of Mallophaga, belonging to the family Philopteridae, which have up to the present been listed under two separate genera, representing two subfamilies. The hosts of the three species under consideration all belong to the Charadriformes. For the present, three species only are included in this new genus, but it is probable that certain other already described species may ultimately have to be transferred to it.

Cunliffe (1921) has shown that the various stages of Ornithodoros moubata may be distinguished by slight differences in the shape of the spiracles. Nuttall, Cooper and Robinson (1908) have described in detail the structure of the spiracles of another tick, Haemaphysalis punctata. Otherwise the spiracles of ticks have received little attention except from systematists, and though Nuttall and his collaborators described a closing mechanism in Haemaphysalis, no study of its function was made. In this paper I propose to describe the structure of the spiracle of Ornithodoros moubata, and show how its function may be investigated by experiments.

Prepupae and pupae are shown to lose weight more rapidly at low than at high humidities. This more rapid loss of weight is due to loss of water alone and not to loss of dry matter.

The limits of temperature and humidity which each of the two stages can survive have been mapped out. If the metamorphic period as a whole is considered, it is likely that the limits of temperature and humidity for survival and development will be narrower than for each stage considered alone.

The length of life at various humidities of unfed flies and of flies fed for 1 day and 6 days on diets of meat, sugar and water, sugar and water, meat and water, and water alone, is discussed. The continued feeding of flies on a diet of meat, sugar and water brings about a shortening of their life at all humidities when the flies are starved owing to their increased rate of metabolism. Flies fed on sugar and water are more resistant to humidity than flies fed on meat, sugar and water, and the females are more resistant than the males. Flies fed on meat, sugar and water lose weight more rapidly than flies fed on sugar and water.

High humidity is more favourable for growth of the ovaries than low humidity. Humidity has no effect on oviposition at temperatures of 10–35° C., but at 40° C. low humidity is unfavourable.