The follwing descriptions relate to two new species of the genera Haemaphysalis and Amblyomma, respectibely, and to a new variety of Amblyomma variegatum:

Haemaphysalis silacea sp. n. ♀, from South Africa (370).

Amblyomma variegatum var. n. nocens, ♂, from South Africa (371).

Amblyomma fiebrigi sp. n. ♂ and ♀, from South America (6).

1. Crithidia pulicis, n. sp., is a parasite of the alimentary tract of the human flea, Pulex irritans.

2. The fleas used in this investigation were bred to the third generation in special “flea cages” on the human body. “Wild” fleas were examined and yielded the same parasite. Both larvae and adult fleas were examined.

3. C. pulicis exhibits pre-flagellate, flagellate and post-flagellate stages in its life history and these phases gradually develop, the one from the other.

4. The flagellate form is very active, movement being accomplished by means of the myonemes of the membrane and body.

5. Pre-flagellates (figs. 1−8) are oval bodies, from 2·3 μ to 7 μ long by 1·5 μ to 4·5 μ broad. The nucleus contains much chromatin and a small karyosome may be present. The blepharoplast is large. The flagellum develops from a chromatophile area. The rate of acquisition of flagellum and membrane varies in individual parasites. Division rosettes are frequent. The pre-flagellates have a somewhat frail appearance.

6. The flagellates of C. pulicis (figs. 9−17) are 26 μ to 65 μ long. Their cytoplasm is richly but finely granular, the nucleus well marked, the blepharoplast large, showing slight variations in shape. Chromidia may be present. The undulating membrane is large, well marked and possesses myonemes which can be detected in the living organism. The free flagellum is relatively short.

7. Post-flagellates (figs. 23−36) are from 3 μ to 6 μ. by 2·0 μ to 4·6 μ. They occur in the rectum and dejecta of the fleas. They are produced by concentration of the protoplasm round the nucleus and blepharoplast with absorption of the membrane and flagellum and finally the production of a thin varnish-like coat.

8. Longitudinal division (figs. 15−22) is the method of multiplication. It occurs in the pre-flagellate and flagellate stages. It may be symmetrical or asymmetric. Division is initiated by that of the blepharoplast, followed by that of the flagellum, membrane and nucleus and finally the body cytoplasm. Two types of asymmetric division have been observed.

9. The method of infection is contaminative, the post-flagellates in the faeces being the source of infection. There is no evidence of hereditary infection.

10. Crithidia pulicis is a member of the genus Crithidia, and is a true parasite of the insect, Pulex irritans.

In a recent paper (Journal of Parasitology, 1910, III. pp. 245—54) I described a new trichomonad (Trichomastixc trichopterorum) and a spirochaete from the hind-gut of certain trichopterous larvae. I also mentioned the occurrence along with these parasites of another peculiar flagellate, which, at the time, I was disposed to consider as closely related to Macrostoma caulleryi, Alexeieff.

1. In accordance with the views held by Chatton and Alilaire (1908) and by Roubaud (1909), I have seen that a true trypanosome-stage occurs in the life-history of Crithidia calliphorae. These try-panosomes have an undulating membrane and cannot be considered as herpetomonads with their blepharoplasts situated behind the nucleus and a completely internal flagellum (Woodcock), nor are they herpetomonads with the flagellum bent back along the body of the cell (Mackinnon). This existence of a trypanosome stage in the life-history of Crithidia is quite comprehensible if we consider that in many cases true Trypanosomata are changed into Crithidiae when they pass from the blood into the gut of an invertebrate host (T. gambiense, T. lewisi, Schizotrypanum cruzi, etc.).

2. There is no sharp difference between the genera Crithidia and Herpetomonas. In Crithidia calliphorae forms may be observed without any trace of an undulating membrane (Diagram I, Fig. 1); in Herpetomonas calliphorae such an organellum may be sometimes present (Diagram IX, Fig. 4).

Still I think that it is not permissible to throw these two genera together, as, generally speaking, an undulating membrane is present in Crithidia and absent in Herpetomonas.

3. Herpetomonas is often biflagellate, even when no signs of cellular division are present and the flagellates multiply less actively than in monoflagellate stocks. Still I agree with Patton that this biflagellate condition is too inconstant to permit of its being recognized as of generic significance.

4. The structure of the blepharoplast of Herpetomonas is distinctly like that of a nucleus, with peripheral chromatin and one or more central granules. It is true that the behaviour of these granules during the division is not so regular as that of the karyosomes of real nuclei, nevertheless, I think that the aspect of the blepharoplast of H. calliphorae is a strong argument in favour of Schaudinn's, and also Minchin's, view that this organellum must be regarded as a specialized nucleus (kinetonucleus).

5. The flagellum of Crithidia calliphorae is constructed in the same way as that of Trypanosoma lewisi: a basal granule is present and the new flagellum is formed by the production of a new flagellar root by fission of the basal part of the old flagellum. In Herpetomonas calliphorae a basal granule (at the base of the flagellum) and a marginal granule (at the point where the flagellum reaches the surface of the cell and becomes free) are present. The part of the flagellum situated between these two granules is the rhizoplast. The marginal granule first divides; then follows the fission of the rhizoplast and basal granule; lastly, from the marginal granule a new flagellum grows out, so closely entangled with the old one that it often seems as if the production of the new flagellum occurs exclusively by fission.

6. The extranuclear chromatoid granules of H. calliphorae consist of volutin. They are numerous during the preflagellate stage and disappear gradually during the flagellate stage; in the post-flagellate stage they are few in number or altogether absent.

This behaviour suggests that volutin in H. calliphorae may act as a sort of nutritive reserve-substance. In degenerating individuals the volutin granules become extremely numerous, an abnormal condition observed also in Trypanosomata (“ volutinosis ”). Consequently volutin seems to play the double part of a nutritive substance, and product of degeneration; this, however, likewise holds for many other nutritive substances (fat, glycogen, etc.).

7. The blepharoplast of H.'calliphorae shows cyclical changes. During the formation of the post-flagellate stages the achromatic substance is lost and only the chromatic portion remains. The blepharoplast is smallest at this period. The preflagellate stages possess a larger blepharoplast, and this organellum reaches its maximum dimensions during the flagellate stage. I am not able to say whether or not these cyclical changes have any special importance; perhaps they have something to do with the regulation of the normal relation between nucleus and protoplasm.

8. H. calliphorae was observed by me only in the gut of the fly and does not seem to be transmitted hereditarily, as is the case in Crithidia melophagia (Swingle, 1909; Porter, 1910).

The observations recently set forth by Dr Leiper, and by Dr Sambon in a discussion, have led us to re-examine the ova of S. japonicum in the material which we have at hand. This material was described previously by one of us together with a report of some comparative measurements of the ova of this species of trematode furnished by Dr Shiga.

By many observers Negri bodies have been considered to be parasitic in nature (Negri, 1903; Babes, 1907). Williams and Lowden (1906) go further and describe the life cycle of these bodies, regarding them as belonging to the Sporozoa, and give to them the name of Neuroryctes hydrophobiae. Calkins (1910), although he states that the parasitic nature of these bodies is not proven, still evidently inclines to that view. In his criticism of the work of Williams and Lowden he comes to differ from them as regards the classification of the supposed organisms. He thinks that their variable forms, the uninucleate condition, the occurrence of a state of distributed chromatin, and the budding phenomenon, are characteristic not of Sporozoa but of parasitic Rhizopods. His opinion is that the distributed chromatin masses in the Negri bodies are in all probability representative of the idiochromidia which are so characteristic of Rhizopods.

Although the literature on ticks is very extensive, we have failed to find any satisfactory description therein of the process of copulation. Most authors state that the male mouthparts are introduced into the female genital orifice, or vulva, and that this constitutes copulation, leaving it to the reader's imagination to determine how the seminal secretion gains access to the female generative organs. The mechanism of copulation, in other words, remains to be described, and we propose, in this paper, to give an account of what we have observed in Ornithodorus moubata. We shall describe the process in Ixodidae in a later paper, but may state here that, as far as our knowledge goes, it is essentially the same as in moubata, that is, impregnation takes place by means of spermatophores.

(1) About 30% of the O. moubata from Uganda have been found to be immune to infection with S. duttoni.

(2) When infected ticks are kept at ordinary temperatures (about 21°C). the following parts of the body are found to harbour the infection :—gut + contents, sexual organs, Malpighian tubules, excrement.

The following parts were found to be uninfective:—salivary glands, coxal fluid.

(3) When infected ticks are kept at a temperature of about 35°C. for two or three days previous to dissection, all the organs of the body, including the salivary glands, are found to be infective. Moreover the incubation periods that elapse before the appearance of spirochaetes in the injected mice are shorter than in the case of the corresponding experiments with ticks that had not been kept at a high temperature.

(4) No spirochaetes have been detected in any of the organs of infected ticks that had been kept at a temperature of about 21°C. When a tick ingests blood containing spirochaetes, the latter persist in the lumen of the gut for periods varying from a few days up to as long as four weeks; usually, however, they disappear from the gut in the course of nine or ten days.

(5) When infected ticks are heated to a temperature of 35°C. for two or three days, spirochaetes reappear in the lumen of the gut, and also appear in all the organs of the tick, and in the coelomic fluid.

(6) The spirochaetal infection that may follow the bite of an infected O. moubata results from the entrance of the infective material, excreted by the tick whilst feeding, into the open wound caused by the tick's bite. It is not the result of the inoculation of infective material from the salivary glands.

A consideration of the facts presented in the foregoing pages appears to warrant certain conclusions which must, however, be regarded in part as provisional and subject to revision when our knowledge of the various species of ticks has become more extended. The views here expressed may prove of practical use in the study of the Ixodidae.

The Argasidae represent the relatively primitive type of ticks because they are less constantly parasitic than are the Ixodidae. Their nymphs and adults are rapid feeders and chiefly infest the habitat of their hosts. In certain Argasidae (O. moubata and O. savignyi) the disadvantage of their possessing an “active” larval stage has resulted in the development of an “inactive” larva, i.e. the young nymph being the first to suck blood. In O. megnini we have a considerable adaptation brought about by the difficulty there must be in the tick entering the small aperture of the ear more than once. Owing to the Argasidae infesting the habitats of their hosts, their resistance to prolonged starvation and their rapid feeding habits, they do not need to bring forth a large progeny, because there is less loss of life in the various stages, as compared to Ixodidae, prior to their attaining maturity.

The Ixodidae are more highly specialized parasites than the preceding. The majority are parasitic on hosts having no fixed habitat and consequently all stages, as a rule, occur upon the host. In the genus Ixodes we find an adaptation of certain species according to the habits of the hosts upon which they are parasitic. In the species which usually occur upon wandering hosts both sexes are found upon the host, whereas in other species which occur on hosts possessing more or less fixed habitats the males are rarely or never found upon the host. The males of species of Ixodes, both sexes of which occur upon the host, are characterized, as a rule, by the possession of hypostomes with prominent teeth, the reverse being the case in forms wherein the males do not occur upon the host. Where species occur upon a wandering host it is essential, for their propagation in nature, that both sexes should be carried about upon the host.

The present report is an account of observations made in Bagdad during the year 1910 (March to November) on the Oriental Sore as it occurs in this part of the world. Though the sore of Bagdad may not differ very markedly from that of other places, it is so common here that all stages and types of the sore may easily be studied, and such points as the early age of infection, immunity, and duration of the disease are very clearly exemplified. Accordingly, a more or less complete account of this disease of Bagdad, known locally as the Date boil or Arabic “Uchut,” will be given, though descriptions of the sore as it occurs in several parts of the world have been published by other observers. During the investigations various side issues arose, and as these suggest certain interesting points, three sections have been added dealing with (1) the life history of Lankesteria culicis (Ross) a gregarine of Stegomyia fasciata, (2) Haemogregarina canis and its development both in the dog and the tick Rhipicephalus sanguineus, and (3) Her-petomonas muscae domesticae, and other flagellates of the house-fly.

In a recent number of Parasitology, Miss Porter, under the above heading, complains because, in the Zoological Record for 1909 (Protozoa division, p. 60), I put the generic names Crithidia and Herpetomonas in inverted commas, when applied to certain species; on this ground she charges me with allowing my personal opinions to influence me in my compilation of the Record, my opinions being, according to her, “extreme and decidedly opposed to the opinions of those who have worked personally on the parasites in question.” Incidentally, Miss Porter makes it appear that my opinions are extreme and of little or no value.

In the course of an inquiry into the relation between the bionomics of certain insects and epidemic disease upon which I am engaged, the following question suggested itself to me. In the event of a larva becoming bacterially contaminated by means of its food, is it possible that the resulting pupa and imago will still be infected? The only previous work bearing upon this question with which I am acquainted is that of Faichnie, who writes:

Through the courtesy of the Editors of Parasitology I have been favoured with an advance proof of the remarks of Dr Woodcock on a former note of mine relating to the procedure of the Recorder of the Protozoa section of the International Catalogue of Scientific Literature and the Zoological Record. In my article I raised three points. (1) In certain cases where the generic names Crithidia and Herpetomonas were placed in inverted commas in the Catalogue, I stated that no direct evidence existed to justify such a procedure. (2) I protested against such meddlesomeness on the part of the Recorder. (3) I stated that the Recorder, who had not worked on the parasites themselves, held, consequently, extreme views. Dr Woodcock's so-called reply has afforded me considerable amusement and it is a matter of surprise to me that he has been so ill-advised as to write such a poor rejoinder—he must know that he has made no answer to my remarks. That the weakness of his position is well known to him is shown by his recourse to the tactics of vituperation and innuendo, where he remarks that my method of criticism is “not straightforward but, on the contrary, distinctly oblique.” Dr Woodcock has no case and so has adopted metaphorically the old, old method of “abusing the plaintiffs attorney,” in the shape of discussing my own papers on parasites not originally under discussion. I am sorry that one who apparently claims to be an authority is reduced to such second-rate methods. While I regret the necessarily severe character of this, my rejoinder, it is impossible to deal otherwise with the numerous side issues raised by Dr Woodcock.