THE GONOSOME 



43 



of a free polypoid manubrium, which bears a close resemblance to the generative zooid of 

 Dkoryne. It would appear, however, from the observations of Fritz lAlullcr,' and of llaeckcl,Hhat 

 in certain geryonidan medusa; the umbrella is formed by the excavation of a solid spherical embryo ; 

 but it must be noted that neither of these observers had seen their embryo mcdusa> at a period 

 anterior to the commencement of the developing umbrella. 



The parallelism which T have thus endeavoured to demonstrate may be expressed in the 

 following scheme : 



8. Further modifications of the Gono)<oine. 



Besides the great leading differences already described, many others of a more subordinate 

 kind are met with. The adelocodonic gonophore in particular exhibits many special modifications, 

 and presents us with a regular series of gradations in complexity, which throw much light on its 

 morphology. 



The simplest form is jjrobably that which we meet with in the female gonophores of the 

 freshwater llifdra. Here there would seem to be no difl'ercutialion of an ectotheca. while the 



Wiegra. Archiv,' 1859, p. 310. 



Die Familie der Russelquallcn (Gcryonidfe),' 18GfJ. 



