ZOOLOGY. 



CLASS III. GREGARINIDA (Gregarines). 



General Characters of Gregarinida. The largest and 

 best known species of this group is an inmate of the 

 intestinal canal of the European lobster, and was named 

 by E. Van Benedcn Gregarina gigantea (Fig. 18). It 

 is worm-like, remarkably slender, and is sixteen mil- 



Fig. 18. Gregarina gigantea. L, two individuals of natural size. K, the eame 

 much enlarged; n, nucleus. A, the same encysted. B, subdivision of the cyst. C, divi- 

 sion of the contents of cyst into pmnll spheres, observed in another species, ff, the 

 t-pheres enlarged. M. cyst filled \vith pi-Tudoimvicellse, O. After Liebeikulin. 1)F, 

 moner-like young of Cf. (/if/and a. G, II, pseudofilaria stage. /, </, early nucleated 

 forms of Oreganna gigantea. After Van Beneden. 



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 fibrillre comparable to that of the 

 Infusoria. The body-cavity of the Gregarina contains a 



