The parasite which I have here described has a life-history containing two distinct stages: a vegetative stage and a sporogonic stage. During the vegetative period multinucleate individuals divide by irregular schizogony producing young uni- or paucinucleate individuals. During the sporogonic period, a number of trophozoites unite to form an aggregation which becomes encysted. In the encysted individuals (the pansporoblasts) there is an increase of nuclear substance and a reduction of plasmatic substance. The nuclei become arranged in pairs and by successive unequal divisions the pansporoblasts produce the sporoblasts which contain a pair of nuclei each. During the formation of the sporoblasts there is an increase of protoplasmatic substance. The sporoblasts become spores by the thickening of their pelliculae.

At first the spores contain two nuclei, finally they become mononucleate. This must be explained by the fusion of the two nuclei.

This nuclear fusion is probably to be interpreted as a paedogamous autogamy (in accordance with the nomenclature of Hartmann, 1909).

My attention was first directed to this Cestode in 1906 when I was asked to examine several specimens of edible fish which had been exposed for sale in the public markets and had been condemned as human food on account of the presence of obvious, intrusive bodies in the flesh. In three of these cases the muscles of the flesh of the fishes—a Halibut, a Megrim and a Hake—contained cysts which enclosed the larvae of a Tetrarhynchid, and on examination the latter was identified as T. erinaceus from the peculiar nature of the armature of the proboscides. In another case the wall of the stomach of a Halibut was also infected with the same larvae. Acting on an obsolete principle of Border Law the Fish Inspectors promptly condemned the fishes and then caused them to be examined. I do not think there was any valid reason for the condemnation of the articles of food, for I can find no reference in the literature to the presence of Tetrarhynchids in the human alimentary canal, and there does not appear to be any question of a possible communication of a parasite by the consumption, as food, of such infected flesh. Further the number of larvae present was far too few to lead to any emaciation of the fish, or to the likelihood of the production of toxic substances in the flesh of the animal. Nevertheless the Inspectors probably acted in the interests of the public health in condemning such articles of food as contained obvious cyst-like structures in the flesh, as to the precise nature of which they were ignorant, since there is always the possibility that these bodies might be detrimental to the health of those eating them.

The study of the life-histories of digenetic Trematodes is as yet in its infancy. Many new adult forms are described every year, but very little is known of the life-history of any of these. It is even impossible in the majority of cases to say what sort of larval form is characteristic of any group. Having worked for some years at the study of Trematode larvae I thought it would be of some use to bring together all the work so far done on British marine cercariae in order to form a nucleus round which future work may be centred.

Twenty years or more have passed since Kurloff first observed certain vacuoles or cell enclosures in the protoplasm of the large mononuclear leucocytes of the guinea-pig while working in Ehrlich's laboratory. Since then improved staining methods and discoveries in the field of protozoology have made it possible to take new view-points in regard to these cell enclosures which are called Kurloff's-bodies. Therefore it is not with surprise that we find Ferrata, Patella, Goldhorn, Schilling and others believing these bodies to be protozoan in nature. Patella however is the only one who claims to have observed a flagellate develop from a Kurloff-body and of course this observation would put an end to all dispute if it could be verified.

The life-cycle of S. gallinarum may be briefly summarised as follows:

Commencing with the ordinary parasite in the blood of the fowl, the spirochaete grows until it reaches a certain length (16 μ–19 μ) and then divides by the peculiar mode of transverse division described above. This process is repeated and is probably the only method of multiplication of the parasite within the blood. When the spirochaetes disappear from the circulation some of them break up into coccoid bodies which, however, do not usually redevelop in the fowl. When the spirochaetes are ingested by Argas persicus, some of them pass through the gut wall into the coelomic fluid. From this medium they bore their way into the cells of the various organs of the tick and there break up into a number of coccoid bodies. These intracellular forms multiply by ordinary fission in the cells of the Malpighian tubules and gonads. Some of the coccoid bodies are formed in the lumen of the gut and Malpighian tubules. The result is that some of the coccoid bodies may be present in the Malpighian secretion and excrement of an infected tick and when mixed with the coxal fluid may gain entry into another fowl by the open wound caused by the tick's bite. They then elongate and redevelop into ordinary spirochaetes in the blood of the fowl, and the cycle may be repeated.

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).