THE GONOSOME. 



31 



discovered by Hincks, and in the nearly allied Eleutheria of De Qnatrefages, whose trophosome 

 has not yet been detected. 



While all the leading features of a gymnophthalmic medusa are thus at once obvious in the 

 phanerocodonic gonophore, the adelocodonic gonophores, on the other hand, present the niedusoid 

 structure only in a disguised or undeveloped condition. They have the form of sacs, and, except 

 in a single known instance, the whole gonophore remains permanently attached to the hydro- 

 soma, giving rise within it to the generative elements, which, after attaining a certain degree of 

 maturity, are ultimately discharged from its cavity. The single exception is afforded by the 



Fig. G. 



Flo 5 



Ambulatory Medusa of Claiaiella pioJ /era 



Free locomotive eporosac of Dicoryne. The figure 

 represents two aspects of the female sporosac when 

 swimming in the open sea, and viewed in planes at right 

 angles to one another. 



genus Dicoryne, Allm. (woodcut, fig. C), in which, before discharging its generative products, the 

 gonophore liberates itself from its external investment or ectotheca, and thus, becoming a free 

 planoblast, swims about actively by the aid of vibratile cilia. 



The following tabular view will exhibit at a glance the various parts which may occur in a 

 hydroid gonosome : 



f f- Adelocodonic or 



I sacciform 

 [Sporosacs) 



2 -i 



Zooids directly sexual 

 [Gonophores] 



Zooids not directly sexual, 

 but giving origin to 

 sexual buds. 



1 fixed. 

 I natatory. 



"1 



L 



Phanerocodonic or 

 medusiform 

 L (Gonockeines). 



f Medusiform 



[Blastochemes] 



I Styliform 



L [Blastosiyles] 



natatory, 

 ambulator}'. 



natatory. 



fixed. 



!■ PlaiKjIjIasts. 



Whether the gonosome remains during its whole lifetime connected with the trophosome, or 

 detaches itself as one or more independent zooids, it is manifest that it constitutes an essential 



