OBSERVATIONS OX FEßÖH- WATER TOLYZOA. HI 



tentacles of tlie una! side, presumably at their tips, althonah I ;im 

 imaljle to prodnce any positive proof. The pores, if ever present, 

 must be of very minute size, indiscernible by ordinary methods in a 

 manner analogous to the pores at the tip of Actininu tentacles, 



5. Muscular System, 



The mnscnlar system consists of live groups of muscles. They 

 are : 



a. Muscles of the funiculus. 



h. Pariet<i-vaoinal muscles. 



f. Retractor of the polypide. 



(L Muscular layer of the alimentary canal. 



e. Muscular layer of the endocysl. 

 T(^ these may be added the muscles of the e[)istonie. 



Tlie first three are, as development shows, moditications of the 

 last two, which in turn may be regarded as only locally differentiated 

 forms of one and the same layer. 



In the develo})ment of the polypide in the statoblast, the muscidar 

 fibres are formed from certain cells of the granular mass, and, in the 

 process of budding, from the lining epithelium. In either case, the 

 cells elongate, and become spindle shaped, with the nucleus at the 

 middle. They lengthen more and more and the nuclei become indis- 

 cernible, although these can often be made visible l;)y the aid of 

 acetic acid. Excepting some fibres of the parieto- vaginal muscles, 

 which remain in this state to the end, the muscular fibres are ex- 

 tremely thin, and do not sliow nuclei in tlieir interior. It seems that 

 these fine fibres arise by the longitudinal splitting of tlie original 

 muscle-cells, as is known to take place in many other animals. 



The muscles are never striated. Even in the retractor of the 



