In an earlier paper (Nuttall, Fantham and Porter, 1909, Parasitology vol II. pp. 325—340), we recorded our observations on living Theileria parva as seen in the peripheral blood of two cows which succumbed to East Coast Fever1. We now propose to describe our studies upon the parasite in stained preparations made from the animals' blood during the course of the disease and from their organs shortly after death. We shall confine our attention to the types of parasites encountered within red blood corpuscles or to corresponding types which may be occasionally encountered free in the plasma. The subject of “Koch's blue bodies” will receive attention at a later date.

Since the appearance of Johnston's Catalogue of the British Non-parasitical Worms in the Collection of the British Museum—a work which although not published until 1865 had been completed some ten years earlier and consequently embodies observations made more than half a century ago—the Hirudinea of the British Islands have been largely neglected. Apart from this the interest now being taken in leeches by students of their protozoan parasites and the absence of any recent work upon this group of our fauna seems sufficient apology for the revised descriptive catalogue attempted in the following pages.

In a lecture delivered recently in Cambridge, I had occasion to demonstrate the degenerative changes undergone by P. canis and Tr. brucei in the blood of animals which had been subjected to curative treatment with drugs. These changes have not as yet been depicted. They are, in my opinion, of more than passing interest, since they may help us to distinguish normal from abnormal parasites in untreated animals. Without doubt there occurs a certain death-rate amongst blood parasites under natural conditions; what this death-rate is we do not know, but appearances which cannot be regarded otherwise than as degenerative are not infrequently encountered. On the other hand, there is always a danger that false interpretations may be placed upon abnormal or degenerative forms, and of this I fear there is ample evidence in current literature. In publishing this note I merely desire to draw attention to what may prove to be a useful method of differentiating some of the normal from the abnormal appearances presented by Haematozoa.

The flagellate to be described in this paper was found in the faeces of a native of the Bahamas who was admitted to the Seamen's Hospital, Albert Dock, in October, 1909. In the course of the examination of the perfectly fresh material it was noticed that numerous flagellates were swimming about. They were taken to be Trichomonas but on closer examination they were seen to differ markedly from these. In the character of their movements there was little to distinguish them from Trichomonas except that the undulating membrane so characteristic of this genus appeared to be absent. The body is pear shaped and there are three long flagella directed forwards from the blunt end of the body. By the lashing of these three flagella the animal is drawn along with the blunt end in advance and at the same time revolves upon its longitudinal axis. A very characteristic feature is the presence of a very large cytostome extending from the base of the three flagella towards the posterior end of the body for about one half to two thirds of its length. The movements of the animals were at first so violent that great difficulty was experienced in making out the details of the anatomy, but as the faeces cooled their activities began to abate. It was then seen that the flagella was as long or longer than the body and that the large cytostome was arranged in a slightly spiral manner: that is to say it did not run directly parallel to the longitudinal axis of the body.

The internal organisation of the Ceatoda is described as follows by Sedgwick (1898, p. 246):

“Beneath the cuticle-like outer membrane is a layer of spindle-shaped cells lying at right angles to the surface; their external ends abut upon the cuticle, and their inner ends are prolonged as fibres into the parenchyma. Beneath this layer there is a delicate superficial layer of longitudinal muscular fibres, and next a parenchyma of connective tissue in which strongly-developed bundles of longitudinal muscular fibres, as well as an inner layer of circular muscles, are embedded; both these muscular layers are traversed, principally at the sides of the body, by groups of dorso-ventral muscular fibres.”

Since the publication of Moore and Breinl's paper (1908) a new method of wet fixation has been introduced into the technique of protozoological research. It is generally stated that the old method of drying the blood films and fixing them afterwards in absolute alcohol, destroys the minute details of nuclear and protoplasmatic structure; that the preparations made in this way are wholly misleading and the structures do not correspond to those of the living Trypanosomes. This becomes evident when we compare the figures of Moore and Breinl and of Rosenbusch (1909), who studied Tr. lewisi with the aid of wet fixation in Flemming's liquid, with those of other authors (Prowazek (1905), Wenyon (1908) etc.) who studied the same subject. The structure of the nucleus is very dissimilar with the two methods. The big karyosome observed by the first authors cannot be found with dry fixation; then only one or more minute granules are to be seen.

In the last number of Parasitology (Vol. iii. No. 1) Mr Wenyon has taken exception to an article of mine on the Leucocytozoa, published in Science Progress, October, 1909. It has been a matter of wonder to many protozoologists as well as to myself, why Mr Wenyon did not reply to my article in Science Progress itself, and thereby appeal to the readers whom he accuses me of having misled, for he states (Parasitology, p. 65) that my “survey of the group is inaccurate and contradictory.”