174 Dwellers of the Sea and Shore 



female. In sertularians, sexual reproduction Is a proc- 

 ess not greatly unlike what we have observed in the 

 case of the seaweeds. The sperm cells stream forth 

 Into the water in countless numbers. On reaching the 

 female colonies, they pass through a perforation In the 

 top of the gonangia, seeking the eggs. Only a few 

 are fortunate in finding the ova, however, whereupon 

 fertilization is immediately effected, to be followed 

 later by the development of the embryos. Eventually 

 these embryos grow into ciliated larvae which, on being 

 liberated, swim to some substantial support and pro- 

 ceed forthwith to start new colonies. 



The campanularlan hydroids, to which reference has 

 been made, are many of them similar in naked-eye 

 aspect to the sertularians. Fut they differ quite notice- 

 ably under the glass. Take Clytea (Clytea poterium) 

 for example. What in most sertularians is a horny cup 

 set close to the branch on which it is borne. Is In the 

 case of this animal a stemmed goblet of crystal trans- 

 parency. The goblet, bell-shaped and open at the top, 

 Is smooth around the rim and without the angularities 

 or modulations commonly founci in campanularlan hy- 

 drotheCcT ; but the stem is faintly ringed throughout its 

 length, giving the merest suggestion of an ornamental 

 pattern — In short, the simplicity of its design makes It 

 a fitting support to so chaste a chalice. The hydranth 

 — but how shall I describe the hydranth ? Every goblet 

 contains a cluster of sclntillant tentacles; yet so feeble 

 Is the light they reflect that they look like the pale glow- 

 ings of ghostly stars. Somewhat like the sertularian, 

 the sea oak, this hydroid is a creeping form. The 

 main stem runs rootlike over the stones or seaweed to 



