196 PROCEEDINGS Or THE ACADEMY OF [1884. 



used. These are frequently collected into spherical groups, and 

 one or more may occasionally be seen in the act of circulation 

 or of violent revolution — the result probably of ciliary currents 

 within the coenoecium. These granular masses adhere to the 

 stomach and other internal organs, obscuring their outlines and 

 making it nearly impossible to detect the appearance of the 

 secondary polypides ; they follow, however, so soon after the first, 

 that it is believed that several heads are considerably advanced 

 before the separation of the valves of the statoblasts. The ten- 

 tacles of the first polypide, however, are generally much better 

 developed when it appears, than are those of the succeeding 

 forms, indicating a nearer approach to maturity. The efi'ect of 

 ciliary action is quite evident in this immature condition, but the 

 cilia themselves are minute and difficult of definition. The gran- 

 ular bodies and groups which obscured the body of the coenoecium 

 become gradually absorbed, or in someway eliminated, remaining 

 latest in the caudal projection and finally entirely disappearing. 



The whole coenoecium then becomes beautifully transparent, 

 disclosing not merely the structure of the individual polypides 

 even when retracted, but the fine lines of the numerous retractor 

 muscles may be readily traced from their connection with the 

 stomach branchia, to their insertion in the disc or opposite 

 portion of the endocyst. The fact that the insertion of these 

 muscles occur in nearly parallel or radial lines upon the disc of 

 the coenoecium may account for the term used by writers who speak 

 of the cells of the coenoecium ; but there are no cell walls, and, 

 when entirely retracted, the stomachs of the individual polypides 

 pass through the lines of muscular filaments and lie wherever the}^ 

 can find room. This " finding room " for their several personalities 

 is often a matter of considerable difficulty to them, and of no little 

 amusement to the observer, who, when a colony is disturbed will 

 seethe first few polypides retire with some appearance of graceful 

 ease, but the laggards must struggle to tuck themselves into a 

 bed where six or eight are already lying, and repeated jerks and 

 jostles are necessary before they can finally hide themselves, as 

 they seem to think, by drawing the transparent coverlid of the 

 endocyst together over their heads. 



The cells of the outer layer of the endocyst are in this genus 

 larger and of greater depth than the corresponding series in 

 Pectinatella ; and in both genera appear to be of the same char- 



