ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 337 



later divide up into a number of flagellate male cells (microgametes). 

 In the first case the result is the self-infection of the host, in the two 

 latter the ultimate result is the infection of new hosts. The macro- 

 gametes are fertilised by the microgametes, and in each case an oocyst is 

 formed round the conjugates. The new nucleus (sporont-nucleus) divides, 

 the daughter-nuclei also divide, and later the protoplasm, so that four 

 sporoblasts are formed within the oocyst. Each of these sporoblasts 

 becomes invested by a thick coat within the original cyst, and thus 

 becomes converted into a sporocyst. Each sporocyst gives rise to two 

 sporozoites, as well as to a residual core of protoplasm. Thus each pair 

 of conjugates give rise ultimately to eight sporozoites. The sexual pro- 

 cess occurs slowly, and the oocyst may be ejected from the host at any 

 stage in development. When taken up by a new host, the coats dissolve, 

 and the sporozoites emerge as sickle-shaped embryos, to begin the life- 

 cycle anew. There is thus a definite alternation of sexual and asexual 

 generations. The cytological characters of each of the different forms 

 is described in careful detail, and comparisons are instituted with the 

 stages of the other species. 



The question as to the natural means of infection is somewhat 

 obscure, for Lithobius is purely carnivorous. Oue method of infection 

 is due to the occasional cannibalism which always occurs where several 

 specimens are kept in confinement. The usual food consists of Oniscus 

 and Porcellio, but it was found impossible to infect these with the para- 

 sites, for the cysts passed unaltered through the body. Nevertheless, as 

 the animals often consume the fasces of Lithobius, the unaltered cysts 

 within their bodies must be regarded as possible sources of infection. 

 As to the effect of the parasites upon the host, it was found that, much 

 as in the rabbit, acute coccidiosis is a disease which runs its course, and 

 from which spontaneous recovery occurs if the animals are able to with- 

 stand the acute stage. This is due to the fact that the process of asexual 

 reproduction has its limits, and no longer occurs after a certain period. 

 As sexual reproduction does not result in auto-infection, the host ulti- 

 mately becomes free from parasites, and the injured intestinal epithelium 

 is regenerated. 



Special mention should be made of the figures, especially of an 

 admirable diagram of the life-history. 



Alternation of Generations in Sporozoa.* — Dr. F. Schaudinn ex- 

 pounds the life-history of Coccidium and Proteosoma, showing (a) the 

 probability of close relationship between Coccidia and Hasmosporidia, 

 and (&) the occurrence of a genuine alternation between sexual and 

 asexual generations. 



New Gregarine.f — MM. L. Leger and 0. Duboscq record that in 

 the mid-gut of Gryllomorpha dahnatina Ocsk. they always found a 

 Gregarine belonging to the genus Gregarina Duf. (Clepsidrina Hamm.). 

 It is a neighbour of G. macrocephala Schm., and of Nemobius sylvestris 

 Eabr., but is specifically distinct. The authors propose the name 

 G. davini for it. 



* SB. Ges. Nat. Freunde Berlin, 1899, pp. 159-78 (11 figs.). 



t Arch. Zool. Expe'r., vii. (1899) Notes et Revue, pp. xxxviii.-xl. (1 fig..) 



June 20th, 1900 2 A 



