INTRODUCTION'. XXXV 



floating in the nutrient fluid, and finds that large numbers 

 of them are derived directly from the tissue which he has 

 named endosarc are indeed the cells of this tissue, some- 

 what modified in shape. He has seen the latter, on the 

 endosarcal cord which traverses the stem of the Ctenosto- 

 mata, exhibiting the precise form and structure of the 

 floating corpuscles, and on the point of detaching them- 

 selves from the cord. In some cases they are round or 

 slightly oval, and consist of a delicate membrane and 

 transparent contents, in which one or more very minute 

 and refringent granules are present. In other cases the 

 membranous envelope incloses a compact mass of granules, 

 which are often set free by the rupture of the sac and 

 swarm in the perigastric fluid. These floating cells, 

 emitted from the substance of the endosarc, Joliet com- 

 pares to the blood-corpuscles of the lower animals. 



THE Ex DOS ARC. 

 ( = the " colonial nervous system " of Fritz Mttller.) 



We have not yet exhausted the contents of the peri- 

 gastric cavity. Besides the muscular bands which pass 

 from the cell-wall to the body of the polypide, we find a 

 contractile cord connecting the base of the stomach with 

 the lower part of the cell, which is known as the "funi- 

 culus" (Woodcut, fig. xix./)*. 



This structure is not only connected with the lower 

 extremity of the digestive sac, but spreads for some dis- 

 tance over one side of it, and not unfrequently gives off 



* The funiculus probably asmsts in the retraction of the polypide, draw- 

 ing the stomach down toward* the bottom of the cell ; it also serves to keep 

 this organ in its proper position when the polypide is expanded. 



(12 



