ZOOLOG r. 



CLASS III. GREGARTNIDA (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 Beneden Gregarina giyantea (Fig. 18). It 

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



Fig. IS. Gregarina r/igant.ea. L, two individual* of natural size. K. the same 

 much i-nlai-ired: . nucleus. A. the name encysted. B, subdivision of the cyst. C, divi- 

 sion (if the contents of cyst into small sphered, observed in another species. N, the: 

 spheres enlarged. M. cyst filled with p.-eudoiiavicella?, 0. After Lieberkuhn. 1) F,. 

 moner-Iike young of ff. <ji ft/itia. G. //, pseudofilaria stage. /, J, early nucleated 

 forms of Greganna yiganteu. After Van Beneden. 



li metres (over half an inch) in length, being the largest, 

 one-celled aniirml 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. I>cneath this outer wall 

 is a continuous layer of contractile substance, forming a 

 true system of muscular fibrillas comparable to that of the 

 Infusoria. The body-cavity of the Gregarina contains a- 



