176 Dwellers of the Sea and Shore 



the middle of the convex side, recalls what we have 

 observed in another place regarding the strobila of the 

 large jellylishes. When, at maturity, the cover of the 

 zooid ruptures, the tiny jellyfishes are liberated. From 

 the inside center of a swimming bell thus set free de- 

 pends the stomach of the creature, having at its outer 

 end a four-cornered mouth. Diverging from the point 

 where the stomach is attached are four tubular canals 

 in the bell which are continuous with a circular canal 

 running around the rim. This is usually a conspicuous 

 feature, and often serves as an aid to identification. 



When a hydrold is in the jellyfish stage, It may be 

 said to have reached the highest point In its develop- 

 ment; for it is only in the mature medusa tliat sexual 

 reproduction occurs. The eggs are pear-shaped ciliated 

 bodies, which are dispersed by the parent meduss at 

 the end of summer ; they swim or drift around until they 

 reach a favorable anchorage; whereupon they grow 

 into hydrold colonies which In turn give rise to other 

 jellyfishes in the following spring. Some meduScT, In 

 addition to their egg-bearing capacity, can reproduce 

 by budding, producing smaller individuals on the 

 stomach or on the rim of the bell. Moreover, not all 

 campanularians are positively known to be of the above 

 described type. Many of these hydroids have not yet 

 been observed to bear medusa cups; nor can all the un- 

 doubted hydrold medusa.^ be identified with the polyp 

 colonies from whence they came. What Is more, some 

 live always in the medusa state, having no colonial 

 existence whatever. 



The plumularians, as the name would indicate, are 

 featherlike hydroids — at least they were when this 



