DEVELOPMENT OF JELLY-FISHES. 63 
nervous system is present in the guoride and Ayinide, 
but is most distinct and best developed in the Geryonide 
(Glossocodon and Carmarina). 
The Hertwigs have also observed in these Trachynemida 
organs of taste, consisting of groups of long stiff hairs at 
the base of the tentacles. They have been observed in 
Rhopalonema velatum, Aglaura nemistoma, and in Cunina, 
where the hairs are shorter. 
The eggs, in developing, after total segmentation (morula 
state) pass into a ciliated planula state as in Awrelia, 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- 
xenia and Aginopsis, where there is a decided metamor- 
phosis, 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 Trachymeduse connect the cov- 
ered-eyed meduse with the naked-eyed or Hydroidea. The 
American forms are found from Newport southward. A 
probably exotic fresh-water form (Limnocodium) lives in a 
tank (90° F.) at London. Cunina has been found by 
Haeckel growing on the columella of Geryonia, and 
McCrady has found that our native Cunina is parasitic on 
Turritopsis, a hydroid medusa. 
The Lucernarie, or Calycozoa, which, accerding 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, Lucernaria 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 
