28 ZOOLOGY. 
Crass III.—GREGARINIDA (Gregarines). 
General Characters of Gregarinida.—The largest and 
pest known species of this group is an inmate of the 
intestinal canal of the European lobster, and was named 
by E. Van Beneden (Gregarina gigantea (Fig. 18). It 
js worm-like, remarkably slender, and is sixteen mil- 
Fig. 18.—Gregarina gigantea. L, two individuals of natural size. K, the same 
much enlarged; n, nucleus. A, the same encysted. B, subdivision of the cyst. C, divi- 
sion of the contents of cyst into small spheres, observed in another species. WN, the 
spheres enlarged. J, cyst filled with Fg hoo pr he 0.—After Lieberkuhn. D—F, 
moner-like young of G. gigantea. 
f ose reac stage. J, J, early nucleated 
forms of Gregarina gigantea.—After Van ‘ 
neden. 
limetres (over half an inch) in length, being the largest 
one-celled animal 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 fibrille comparable to that of the 
Infusoria. The body-cavity of the Gregarina contains a 
* Excepting of course the larger Foraminifera. 
