IV 



INTRODUCTION. 



STOLON. The creeping tubular stem, by which the 

 individual zooccia or celliferous shoots composing a colony 

 are held together, in certain members of the class (e. g. 

 the Ctenostomata] . 



GENERAL PLAN OF STRUCTURE. 



In every polyzoon we distinguish two fundamental 



elements, the zocecium and the polypide. These are the 



Fig. i. 



S. Membranous sac. f. Tentacular crown. o. Mouth. ov. (Eso- 

 phagus, st. Stomach, int. Intestine, a. Anus. //. Nervous 

 ganglion. /. Funiculus. ov. Ovary, sp. Spermary. 



primary zooids in every colony. When the larva fixes 

 itself, after its brief term of free life, it is metamorphosed 



cell of Crisia and other forms, and the superficial inflation of tho zoarium 

 in which the embryos are developed in many of the Cyclnstomata. It is 

 clearly desirable, however, that thow very different strudurcs should be 

 distinguished by separate names. 



