636 



INVERTEBBATE MORPBOLOGT. 



almost the entire length of one side of the body and leads into 

 a branchial sac whose stigmata open directly to the exterior, 

 the atrial cavity disappearing during the course of develop- 

 ment. The intestine is well developed, but the muscles are 

 but slightly indicated, while the reproductive organs, rudi- 



1 g 



Fig. 291. — A, The Non-bexual, and B, the Sexual, Form op Boliolwn 



(after Uliahin). 



cZ = cloaca. j = intestine. 



dp = dorsal process. n ^ nerve-ganglion. 



en = endostyle. ot = otocyst. 



g = reproductive organ. ph = pharynx. 



h = heart. st = stolon. 



ments of which were present in the young buds, completely 

 atrophy during the process of development. These buds 

 are incapable of leading a free existence, serving only as 

 nutritive and respiratory individuals for the median buds, as 

 ■well as for the parent, whose digestive tract degenerates, its 

 muscle-bands and nervous system at the same time under- 



