212 



ZOOLOGY 



from the parent, and the eggs develop in the bud. In 

 still other cases a mere bud, called gonophore, is formed, 

 which becomes full of sexual products without ever ac- 

 quiring resemblance to a jelly-fish. The jelly-fish is the 

 primitive type which has undergone a reduction in some 

 cases to a gonophore. It is an interesting fact that in 

 certain species sometimes jelly-fishes and sometimes gono- 

 phores will be produced. In the Campanularidae the 



FIG. 199. Zygodactyla. Reduced. From a drawing by A. Ajjassiz. 



gonophores are encased in a cuticular capsule, but in the 

 Tubularidse they are quite naked. 



There are certain hydromedusre in which the hydroid 

 stage is unknown or known to be lacking. Here belong 

 some jelly-fishes of large size, like Zygodactyla, one of the 

 Trachomedusse of our coast, which may become eight to 

 ten inches in diameter (Fig. 199). Besides these the sea 

 contains many small species, which are easily captured in 

 the net, and which are of extreme beauty and delicacy. 



Besides the Hydromedusre, the group of Hydrozoa in- 

 cludes the Siphonophora. 1 These animals are always 

 colonial and free-swimming, and are among the most 



1 0-/0WJ/, a siphon ; </>o/)6s, bearing. 



