28 



ZOOLOGY. 



CIASS III. GREOARTNIDA (Gregarines). 



General Characters of G-regarinida. The largest and 

 best known species of this group is tin inmate of the 

 intestinal canal of the European lobster, and was named 

 by E. Van Beneden Greganna yiyantea (Fig. 18). It 

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



Fig. l$.Gregarina qigantea. L, two individual* of natural size. K, the same 

 much enlarged; , nucleic. A. the same encysted. B. subdivision of the cyst. 0, divi- 

 sion of the contents of cyst into small spheres, observed in another species. JV. the 

 spheres enlarged. M. ry*t filled with pseudonavicellse, 0. After Lieberknhn. D F. 

 moner-liko young of (f. gigantea. G, H, psuudofilaria stage. /, .7, early nucleated 

 forms of G'regwina yigantea.-A.fter 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 Avail 

 is a continuous layer of contractile substance, forming a 

 true system of muscular fibrillse comparable to that of the 

 Infusoria. The body-cavity of the Gregarina contains a 

 * Excepting of course the larger Foraminifera. 



