SPOROZOA 



99 



syngamy or spore-formation ; sometimes from two to five may 

 be aggregated into a chain or " syzygy." The number of cases 

 in which a syngamic process between two cells has been observed 

 is constantly being increased. In Stylorhynchus (Fig. 33) the 

 conjugation at first resembles that of Monocystis, but the actual 

 pairing-cells are bisexually differentiated into sperms in the one 

 parent, and oospheres in the other ; it is remarkable that here the 

 pear-shaped sperms are apparently larger than the oospheres. In 

 Pterocejrfialus the chief difference is that the sperms are minute. 1 

 In all cases of spore-formation the epimerite is lost and the 

 septum disappears ; in this state the cell is termed a sporont. 

 Sometimes the epiplasm of the sporont forms tubes (" sporoducts "), 

 which project through the cyst- wall and give exit to the spores, 

 as in Gregarina (Fig. 32, C), a parasite in the beetle Blaps. 



Gregarines infest most groups of Invertebrates except Sponges 

 and perhaps Coelenterates, the only exception cited being that of 

 Eirizoanthus glacialis, a Zoantharian (p. 406). They appear to 

 be relatively harmless and are not known to induce epidemics. 



The Coccidiaceae never attain so high a degree of cellular 

 differentiation as the Gregarines, which may be due to their 

 habitat ; for in the growing state they are intracellular parasites. 

 Their life-history shows a double cycle, which has been most 

 thoroughly worked out in Coccidiidae by Schaudinn and Siedlecki 

 in parasites of our common Centipedes. We take that of 

 Coccidium schiibergi (in Lithohius forficatus 2 ), beginning with the 

 sporozoite, which is liberated from the spores taken in with' the 

 food, in the gut of the Centipede. This active sickle-shaped cell 

 (Fig. 34, I) enters an epithelial cell of the mid-gut, and grows 

 therein till it attains its full size (), when it is termed a 

 " schizont " ; for it segments (Gk. cr^o>, " I split ") superficially 

 into a large number of sickle-shaped zoospores, the " merozoites " 

 (c), resembling the sporozoites. The segmentation is superficial, 

 so that there may remain a large mass of residual epiplasm. 

 The merozoites are set free by the destruction of the epithelium- 

 cell in which they were formed, and which becomes disorganised, 

 like the residual epiplasm. Each merozoite may repeat the 



1 Leger, Arch. Zool. Exp. ser. 3, x. and ser. 4, v. (1902-3) ; for a full discussion 

 of the relations of association and conjugation in Gregarines, see Woodcock in 

 Quart. Journ. Micr. Sci. 1. 1906, p. 61 f. 



2 A Lithohius is figured in Vol. V. p. 45. 



