GREGARINIDA 



6 7 



which is also the only genus that forms more than eight sporozoites 

 fig. 25, a). The form and size of the spores vary considerably according to 

 the species, and afford a valuable means for their distinction (figs. 25, b-e). 



The development of the spores within the cysts generally takes place 

 outside the host in the open, and may occupy very variable times. The 

 cysts discharge their contents the spores either by simple bursting o/ 

 the envelope of the cyst, or with the assistance of the swelling residual 

 body, or by means of particular invertible sporoducts, one or several of 

 which appear on the envelope of the cysts. 



The ingestion of liberated spores, or also of mature cysts, causes infec- 

 tion. The sporozoites are actually only young gregarines, which become 

 free through the bursting of the spores, acted upon by the intestinal juice, 

 and in many cases bore into the epithelial cells of the invaded intestine 

 by means of peculiar movements, which, however, are not amoeboid. 1 In 



c. 



FIG. 26. Development of Clepsidrina longa. (a) Occupying the epithelial cell ; 

 (b, c) gradually coming out ; (d) attached by the clinging apparatus ; (e) fully 

 developed. (After Leger.) 



this situation they increase in size, and grow beyond the epithelial cells 

 occupied by them ; the nucleus then lies in that part of the body extend- 

 ing from the cells into the intestinal lumen ; the posterior extremity of 

 the parasite, the deutomerite, is then separated from the anterior extremity 

 by a transverse partition, and this part is finally divided into the epi- 

 and proto-merit (fig. 26). In the gregarines inhabiting the abdominal cavity 

 an intra-cellular stage is wanting, as the sporozoites, which have become 

 free in the intestine, travel through the intestinal epithelium without 

 staying there ; but a few species inhabiting the intestine depart from the 



1 The infected epithelial cells are mostly not visibly altered ; recently, however, 

 cases have become known in which they have become hypertrophied and have finally 

 perished. Laveran and Mesnil, " Sur quelq. particul. de I'evol. d'une greg." (C. R. soc. 

 biol., Paris, 1900, lii., p. 554). Siedlecki, M., " Sur les Yapp. d. greg. avec I'epith. intest. 

 (ibid., 1901, liii., p. 81). Siedlecki, M., " Contrib. a I'etud. d. chang. cellul. prov. p. 

 1. greg." (Arch, d'an. micr., 1901, iv., p. 87). Leger et Dubosq., " Not. sur les grillons. 

 III. Gregarina Davini " (Arch. Zool. exp., 1899, ni - ser - 7 / not - et revue, p. 38). 



