DEVELOPMENT OF JELLT-FI8EE8. 63 



nervous system is present in the ^quoridcB and JEginidm, 

 but is most distinct and best developed in the Geryonidm 

 {Glossocodon and Carmarina). 



Tlie Hertwigs have also observed in these Trachjuemidse 

 organs of taste, consisting of groups of long stifE hairs at 

 the base of the tentacles. They have been observed in 

 Rliopalonema velatum, Aglaura neniistoma, and in Cunina, 

 Tvhere the hairs are shorter. 



The eggs, in developing, after total segmentation (morula 

 state) pass into a ciliated planula state as in Aurelia, there 

 being at first apparently no primitive gastric cavity ; the 

 body of the embryo or planula remains spherical, as in Gery- 

 ■onia, there being a slight metamorphosis ; or, as in Poly- 

 ^enia and JBginopsis, where there is a decided metamor- 

 j)hosis, the spherical ciliated planula greatly lengthens out 

 on each side, the body becoming boomerang-shaped, each 

 •end of the boomerang becoming an arm or tentacle. Then 

 it becomes a gastrula, a central cavity and mouth appear- 

 ing. At right angles to the two primitive arms bud out 

 two others, and finally others appear on the lower edge of 

 the umbrella, and after slight changes the adult form is as- 

 sumed. Cunina is at first spherical, then, a single arm 

 ■developing, it becomes club-shaped ; finally, the full num- 

 "ber of arms grow out, and the mature form results. It ap- 

 pears, then, that in the mode of development from eggs, 

 ■without passing through a hydra-like condition, and in the 

 structure of the body, the TrachymeduscB connect the cov- 

 ered-eyed medusae with the naked-eyed or Hydroidea. The 

 American forms are found from Newport soutliward. A 

 probably exotic fresh-water form (Limnocodium) lives in a 

 tank (90° F.) at London. Cunina has been found by 

 ilaeckel growing on the columella of Geryonia, and 

 McOrady has found that our native Cimina is parasitic on 

 Turritopsis, a hydroid medusa. 



The Lucernarim, or Calycozoa, which, according to Clark, 

 form an order of Acalephs, are, with Huxley, regarded as 

 a suborder of Discophora. With essentially the structure 

 of the Aurelia and allies. Lucernana differs in having the 

 power of attaching itself by a sucker on the smaller end of 

 its body to sea-weeds, but can detach itself at will and swim 



