The foregoing comparison of the anatomy of the apterous viviparous and the winged viviparous stages of S. rosarum although not revealing any very great differences, may be regarded as supporting the view that the apterous stage is a degeneration from the winged stage. The fact that so much similarity exists between the two forms is perhaps more easily explained by supposing that the habit of flight had become eliminated, possibly through disuse, resulting in the consequent atrophy and disappearance of the organs directly concerned with that function; for if the other view be considered, it would be reasonable to suppose that more specially marked differences in an upward direction would be the result of such a vital change in the habit of the creature. There is one point of difficulty, however, and that is to account for the difference in form of the alimentary canal, but, as has been already suggested, this may be due to other, quite different, and at present unknown, causes.

1. All the bacilli hitherto investigated, when growing on the surface or in the depth of agar, exhibit “post-fission” movements after division.

2. Four types of post-fission movement have been noticed, which may be termed “loop-forming,” “folding,” “snapping” and “slipping.”

3. These types of post-fission movement seem to depend on the strength, adherence and mode of rupture of the capsule. In the “loop-forming” group the capsule is very strong and adherent and is very seldom ruptured. In the “folding” group the portion of the capsule uniting the adjacent bacilli in the chain is long and flexible. In the “snapping-group” the capsule seems to undergo partial rupture at the time of division, and in the “slipping” group it is completely ruptured.

4. “Loop-forming” post-fission movements are shown by B. anthracis, “folding” by B. pestis and certain organisms morphologically resembling B. anthracis, “snapping” by all diphtheroid organisms and “slipping” by organisms belonging to the typhoid-enteritidis-colon group, vibrios, the butter bacillus (Rabinowitch), B. pyocyaneus, B. fiuorescens, B. subtilis and allied organisms and many non-pathogenic species.

5. The characters of the colonies formed by organisms exhibiting loop-forming, folding and snapping post-fission movements are not markedly altered by the condition of medium under ordinary conditions of cultivation. When thickly sown on moist agar continuous growths are formed by all of them, but the edges of these growths resemble the edges of the separate colonies. All organisms exhibiting slipping post-fission movements form films on moist agar. Under unsuitable conditions for film formation the larger and stronger members produce either colonies with radiating processes on moderately moist agar, or rounded colonies on dry agar. The smaller, weaker, and slower growing members produce colonies which to the naked eye appear more or less rounded.

Most of the specimens described in the following notes were collected by the International Fishery Commission's S.S. Huxley, in the North Sea, during the years 1905–09. They were preserved in dilute formalin in sea water, or in Bles's Fluid. Owing to the length of time during which the specimens had remained in the preservative, and in some cases owing to their large size, the fixation and preservation were not in every case as perfect as might have been wished, so that many of the finer histological details could not always be determined.

A good deal of doubt still exists in many quarters as to the exact meaning of the term Leucocytozoon applied to certain Haematozoa. The term Leucocytozoaire was first used by Danilewsky in writing of certain parasites he had found in the blood of birds. In a later publication he uses the term Leucocytozoon for the same parasites though he does not employ it as a true generic title. In this latter sense it was first employed by Ziemann who named the parasite of an owl Leucocytozoon danilewskyi, thus establishing this parasite the type species of the new genus Leucocytozoon. It is perhaps hardly necessary to mention that Danilewsky and Ziemann both used this name because they considered the parasite in question to inhabit a leucocyte of the bird's blood. There has arisen some doubt as to the exact nature of this host-cell. Some authorities consider it to be a very much altered red blood corpuscle, some perhaps more correctly an immature red blood corpuscle, while others adhere to the original view of Danilewsky as to its leucocytic nature. It must be clearly borne in mind that the nature of the host-cell does not in any way affect the generic name Leucocytozoon. If it could be conclusively proved that the host-cell is in every case a red blood corpuscle the name Leucocytozoon would still remain as the generic title though it would have ceased to be descriptive.

The value of arsenic in the treatment of trypanosomiasis is no new discovery.

Evans (1880), who described the first pathogenic trypanosome, recommended the administration of arsenic. Lingard (1899), for many years, investigated surra in India and treated twenty-one horses suffering from that disease with arsenious acid. One horse survived. His system of treatment was, the administration of arsenic in the form of Fowler's solution, commencing with 5 grains, twice daily and gradually increasing to 10 grains. Treatment extended over several months; the total amount of arsenic given, in some instances, amounted to over 2,000 grains. During the period of treatment intermissions of 30 to 50 days were recorded, but all the animals, with one exception, finally succumbed to the disease. Bruce (1897 and 1903), treating nagana in Zululand, gave 6 to 12 grains of arsenic in form of arsenite of soda to horses and asses suffering from that disease. Trypanosomes remained absent during the period of treatment, but reappeared immediately treatment ceased. Trélut (1907) claims to have cured cases of dourine by the daily administration of 3 to 6 grammes of arsenious acid. Archangeliky and Novikoff (1907) also record cases of dourine cured by them with arsenite of sodium and cacodylic acid. Marchal (1903) stated that he cured five stallions suffering from dourine by subcutaneous injections of 1 gramme of cacodylate of soda. Loeffler and Ruehs (1908) record a number of successful experiments on animals affected with nagana, which they treated with a solution of arsenious acid. They consider this solution to be a specific cure and a prophylactie for nagana. Laveran and Thiroux (1907–8) repeated these experiments and came to conclusions different form those of Loeffler and Ruehs.

Owing to the courtesy of my friend, Mr W. F. Cooper, B.A., who prepared blood-films and organ smears from various wild animals shot by him in British East Africa in August, 1909, I am in a position to record three new parasites from the Jackal and Buffalo. Mr Cooper prepared the films as soon as possible after the animals were shot, using either absolute alcohol or heat for fixation. On arrival in Cambridge, the films were stained in the usual manner by Giemsa.