HYDROIDS 177 



parallel to each other except toward the proximal end, 

 where irregular cross connections are common. The prox- 

 imal third of the stalk is covered with a thin perisarc, the 

 rest being naked. 



A fairly well marked constriction separates the stalk 

 from the hydranth. The hydranth consists of a thick- 

 ened disc attached to the distal end of the stalk and car- 

 rying on its periphery some twenty to thirty long ten- 

 tacles, the proximal tentacles. Prom the middle of the 

 outer face of the disc rises the proboscis, at the distal 

 end of which is the mouth surrounded by about forty to 

 sixty short tentacles. Immediately beyond the bases of 

 the proximal tentacles, and taking their origin from the 

 proximal part of the proboscis itself, arises a number of 

 short peduncles, to which are attached fixed medusae 

 bearing the gonads. The appearance of Corymorpha as 

 a whole is that of a delicate miniature palm tree whose 

 substance seems to be translucent glass rather than ani- 

 mal matter. 



The common reaction systems possessed by the ma- 

 jority of coalenterates are the mucous glands, the cilia, 

 the nettle cells, and the muscles. In Corymorpha the 

 mucous glands are insignificant and it is very doubtful 

 whether there are any cilia at all. Nettle cells are pres- 

 ent and are apparently quite independent of nervous 

 control. 



The muscles of Corymorpha are few and simple in 

 comparison with those of an actinian and have already 

 been briefly described by Torrey (1904 b). The longitu- 

 dinal muscle of the stalk (Allman, 1871-1872) is a sheet 

 of tissue whose fibers run lengthwise that structure and 

 are closely applied to the ectodennic face of the sup- 

 porting lamella, 



The circular muscle of the stalk: (Allman, 1863) con- 

 12 



