28 



ZOOLOGY. 



CiASS III.— Geegaeinida (Gregarines). 



General Characters of Gregarinlda. — The largest and 

 best known species of this group is an inmate of thfr 

 intestinal canal of the European lobster, and -svas named 

 by E. Van Beneden Gregarina gigmitea (Fig. 18\ It 

 is Tvorm-like, remarkably slender, and is sixteen nul- 



Fig. 18. — Gregarina ctigantea. L, two incUviciurti--. of natural size, K. the same 

 mncli enlarged; n. nucleiw. ,-1. theeame encyjjietl. B, subdivision of the cjrst C, divi- 

 sion v. f the'contents of cyst into small .-phtfiL-. observed in another species. iV. the- 

 spheres enlarged. .V. cyst filled with j)>eufi()iiavicell8e. O. — After Lieberkuhn. !>■ — F, 

 moner-Iike young of (f. gi nnft-a. G. H, pscudolilaria stage, i, J, early nucleated 

 forms of Greganna gigarUea. — After Van Benedon. 



limetres (over lialf an inch) in length, being the largest 

 one-celled anirriiil known. In this organism an external, 

 structureless, perfectly transparent membrane with a double 

 contour can be distinguished. It represents the cell-wall 

 of the cells in the higher animals. Beneath this outer wall 

 is a continuous layer of contractile substance, forming a 

 true system of muscular fibrillffl comparable to that of the 

 Infusoria. The body-cavity of the Gretrarinu contains a, 



