During the past few months we have collected a considerable amount of information relating to the value of pH. as affecting the distribution of the three species of Limnaea commonly found in North Wales. Tables I and II show that L. truncatula occurs over a range of pH. 6·0 to 8·6, and L. peregra 5·8 to 8·8; L. palustris was recorded from 7·4 to 8·0 (but only three of the readings included this species).

In a note which I contributed in 1918 to Special Report, No. 19 of the Medical Research Council, I attempted to show that the “correct” generic name of the spirochaete of syphilis—according to the Rules of Nomenclature—is Spironema Vuillemin, 1905. The premisses from which this conclusion was drawn were briefly set out in the publication cited, and need not be repeated here: but my argument—put very shortly—was that, since the Spirochaetes are Bacteria, and not Protozoa, their nomenclature must be determined by the Botanical Rules, not those of Zoology; and that of the three generic names proposed for the spirochaete of syphilis in 1905, Spironema has priority, and must therefore be accepted. (Spironema was proposed by Vuillemin in June, Treponema by Schaudinn in October, and Microspironema by Stiles and Pfender in December, 1905.)

The systematic position of Nematodes is an old standing problem which has already received much attention from zoologists. The conclusions at which they have arrived are however very discordant and the most widely separated orders of Metazoa have been claimed as near relatives of Nematodes. This great divergence of opinion has not abated the general interest in the problem, but, on the contrary, has had a greatly stimulating effect as was shown recently at the British Association for the Advancement of Science (1923) in a discussion on the affinities of Nematodes, opened by Prof. Hickson and supported by Prof. Goodrich and Dr Baylis. The results of this discussion were soon afterwards incorporated by Dr Baylis in a very interesting paper containing a complete review of the problem as well as a statement of the author's own views.

The term “Myiasis” is generally used to indicate the presence of Dipterous larvae in the living body of man or other animals. “ The form of Myiasis most commonly met with in the United Kingdom,” writes Austen (1912), “is that of the alimentary canal, as the result of which living larvae or pupae, greatly to the distress and alarm of the patient, are discharged from the bowel. Cases of Myiasis of the nasal passages and frontal sinuses the external auditory meatus, the subcutaneous tissue, and the urinary passages are apparently of quite exceptional occurrence in the British Islands.” The following pages deal with three hitherto unrecorded cases, two of urethral and one of intestinal Myiasis.

Since the publication of a paper by Bassett-Smith (1896, Journ. Mar. Biol. Assoc. n.s. IV. 155) a considerable number of new species and other species of parasitic Copepoda has been taken at Plymouth. Bassett-Smith's work forms the basis of this list, but some species are now assigned to other genera, or degraded as synonyms, while in some cases the names of genera are changed owing to preoccupation. Additions have been made by the collections of L. Harrison Matthews and myself.

p. 151, line 9 Read biramous for uniramous (see Fig. 4).

p. 153, line 15 Delete the words in parenthesis.

p. 276, line 6 Read median for medium.

The trematodes described in this paper were collected by Miss Reynolds and myself from Corvus insolens, a Burmese house-crow, specimens of which contained many parasites of different species, all being minute except in two cases. They were obtained by washing the intestines after opening them in luke-warm water in a large glass basin, whence they were removed by means of a pipette, being readily identified owing to their slight movements. Those occurring in the liver were obtained by teasing that organ in luke-warm water. Table I records the results of the examination of five crows for parasites. I am indebted to Miss Reynolds for the help she gave me in placing the material she collected at my disposal.

Leigh-Sharpe (1918, Parasitology, XI. p. 24) states that the alimentary canal of the male has no visible contents and quotes Wilson (1915) to the effect that there is never an anus. He (Leigh-Sharpe) makes three suggestions: (i) that the male never feeds, (ii) that it feeds on the spermatozoa of the dogfish or (iii) on the eggs of the nematode which infests the latter. It is unlikely that the copepod is capable of completely digesting the chitinous case of the eggs in a canal which Wilson (loc. cit.) states to be sparingly furnished with glands; but if there is to be no debris all material taken in must be completely digested and absorbed. If the male never feeds the mouth would degenerate as rapidly as the anus; the mouth and oesophagus are both well developed. That spermatozoa form the food is a suggestion which cannot be disproved except by observation of the living animal.

Habitat and record. The animal under consideration, a copepod of the Family Caligidae, has up to the present received three notices: by Norman and T. Scott (1906), A. Scott (1907), and T. and A. Scott (1913). (For further particulars see References at end of this paper, p. 409.) Norman and Scott stated that “the specimens were taken forty years ago on the dory by Laughrin, and by him sent to A. M. N.” Consequently, the specimens were forty years old before they were described, which would, even in the absence of other reasons, excuse a little scepticism as to the description. Scott gives a bare record of capture, with a copy of Norman and Scott's diagrams. These diagrams and the original of Norman and Scott are republished by Scott and Scott with the addition of a few errors. Considering these facts, and also that no satisfactory description is given of the appendages of the male, or of the maxillae or swimming legs of the female, and that the animal is very common, occurring on nearly every dory, I feel that there is some justification for a further description.

1. Tick paralysis occurs in man, the dog, and other domesticated animals on the East Coast of Australia.

2. As far as is known, the disease in Australia is only conveyed by the mature female of Ixodes holocyclus. The immature stages and the male of this species of ticks are non-pathogenic.

3. A similar disease, induced in a like manner by females of other species of ticks, has been observed by various authors in South Africa, Canada and Crete.

4. A single tick, as shown by experiment, may cause fatal paralysis in man and the dog in Australia, the death-rate in dogs being very high.

5. The main symptoms of tick paralysis in Australia do not differ materially from those observed in other countries. They begin with loss of coordination commencing in the hind legs in dogs, the fore legs, head and neck becoming subsequently affected. Death in all cases appears to be due to respiratory paralysis.

6. The onset of symptoms has not been observed to occur in less than 5 days from the time the tick or ticks have attached themselves to a dog.

7. Some of the ticks do not produce paralysis and others do, as shown repeatedly from my experiments on dogs. This requires explanation. It does not depend on the time that has elapsed between the tick having moulted and its attacking the dog.

8. Paralysis has never been seen to occur when ticks were removed from dogs before the time when symptoms usually appear.

9. It is impossible to transmit the disease from affected to healthy animals by the inoculation of blood, cerebro-spinal fluid or nervous tissue. Nor can the disease be transmitted by the injection of the body contents of ticks removed from affected animals. The examination of the fluids and organs of affected animals has failed to reveal the presence of pathogenic organisms.

10. It is considered that the causal factor in the production of the disease is a tick-derived toxin, this toxin being secreted by the salivary glands.

11. During the process of engorgement the salivary glands develop greatly, pouring out a maximum amount of secretion during the 2 days before the female tick drops.

12. An emulsion of salivary glands of I. holocyclus proved to be toxic for when injected into a dog (Experiment V, p. 424) it caused fever, vomiting, etc. The salivary secretion contains anticoagulins. As Nuttall and Strickland found for anticoagulins, individual ticks may vary in toxicity.

13. The period which elapses between the attachment of a tick to the host and the first signs of an attack of tick paralysis cannot be regarded in the light of an incubation period; it is dependent on the rate and stage of the tick's engorgement.

14. If it be accepted that the causal agent of the disease is a tick-derived toxin, it remains to be shown how such a toxin is produced.

15. There is some evidence that immunity to the disease may be acquired after recovering from previous attacks.

16. There is no evidence of season having an influence on tick paralysis. It was induced experimentally both in winter (June–August) and summer (November–December) in Sydney.

Reference to the National Insect Collection at Ottawa shows that species of the genus Cuterebra have been collected in various localities of Western Canada at different times. Of these Cuterebra grisea Coq. is distributed throughout Manitoba, Saskatchewan, Alberta, North-West Territories and British Columbia. There is one record each of C. emasculator Fitch (determined by Aldrich as C. fontinella Clark), of which the locality is unknown, and of C. fasciata Swenk, from Peachland, British Columbia. The specimen of C. emasculator bears a note that it had been reared from a chipmunk, Tamias striatus lysteri Richardson. The remaining species, C. americana var. polita Coq., C. similis Johnson and C. tenebrosa Coq. have all been collected in British Columbia. There is but a single record from the Eastern Provinces and that a specimen of C. fasciata from Bathurst, New Brunswick, dated August, 1900. Altogether there are 22 specimens in the National Collection belonging to six species. Of these there are 11 specimens of C. grisea, which would thus appear to be the most prevalent species in Western Canada. The comparative paucity of specimens may be correctly attributed to the peculiarly shy habits of the species, the adults of which, according to information furnished me by Criddle, prefer rather dark situations, such as outbuildings, summer kitchens and the ground burrows of rodents. They occur on the wing from June to September and are probably to be found closely attendant upon the haunts of their rodent hosts. That the percentage of parasitism is not high is concluded from the fact that Parker and Wells (1919), in a careful examination of over a thousand rodents in Montana for possible infestation by the Rocky Mountain spotted fever tick, Dermacentor venustus Banks, found but two that were parasitised, each with one larva of C. tenebrosa.

The examination of the rabbits of the Aberystwyth area has shown heavy infection with adult cestodes. Of 516 small intestines of rabbits examined 358, or 66 per cent., have harboured adult cestodes. Two species occur—Cittotaenia pectinata (Goeze 1782) and Cittotaenia denticulata (Rudolphi 1804). Neither appear to have been recorded for the British Isles before. Theobald (1910) refers to reports of the prevalence of tapeworms in rabbits from near Winchester and from Devonshire. The known distribution of C. denticulata is Germany and France, and of C. pectinata, Germany and France and a variety, var. americana, in North America. C. pectinata is found in that part of the small intestine nearest the stomach. C. denticulata occurs in the lower part of the small intestine. On no occasion have the two species been found in one rabbit.