28 



ZOOLOGY. 



Class III.— Greg arinida {Gregarines). 



General Characters of Gregarinida.— The largest and 

 best known species of this group is an mmate of the 

 intestinal canal of the European lobster, and was named 

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

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



Fig. 18. — Gregarina gigantea. Z, two individutils of natural size, ff, ttie same 

 much enlarged; )7, nvicleus. A, the same encysted. 5, Bubdivieion of the cyst. C, divi- 

 fiion of the contents of cyst into Bmall spheres, observed in another species. N, the 

 spheres enlarged. 3/, cyst filled with pseudonavicellee, 0. — After Lieberkuhn. B — F, 

 moner-like young of O. gigantea. ft, H. pseudofllaria stage. 7, ./, early nucleated 

 forms of Greganna gigantea. — After Vau Beneden. 



limetres (oTer 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 fibrillse comparable to that of the 

 Infusoria. The body-cavity of the Gregarina contains a 



