Branch Coelenterata 23 



XI. — Sexual Reproduction. Light-colored blunt processes 

 formed only of ectodermal cells appear on the body 

 near the tentacles. Such structures are the male 

 reproductive bodies and are called spermaries. Their 

 inner cells change into sperms, and when the thin wall 

 holding them bursts, they go forth as free-swimming, 

 pointed masses of protoplasm. 



Xn. — Elevations similar to the spermaries also occur near 

 the basal end of the body. These are the ovaries, and 

 are at first similar in structure to the spermaries. Their 

 inner cells soon disappear, vfith the exception of one 

 large amoeboid cell, called the ovum. This soon be- 

 comes freed from the Hydra, and is penetrated by a 

 single sperm from some other Hydra. The process is 

 called fertilization, and the fertilized ovum sinks to a 

 sheltered place and soon develops into a Hydra. 



You will probably be unable to study this process by 

 actual observation, since it is much more hidden and 

 complex than that of budding. Any slight swellings 

 on the side of the Hydras should, however, be care- 

 fully studied, although it may be hard to distinguish 

 between ovaries, spermaries, and young buds. 



THE (JAMPANULARIAN HYDROID 



HYDRIFORM STAGE 



This little animal lives in colonies in shallow water along 

 the seashore. 



I. — Examine through a hand lens or with the low power 

 the specimen in your watch glass. Notice its general 

 appearance. Is it attached to anything.' Is there 

 any variation in the color .? Observe the size of your 

 specimen. 



