ir 



lip* 



* 



Snnl 



* 



roceadf 



txxi I 









HYDROZOA. 4 1 



urn 



. somatic cavity (fig. 6, a). The proximal ex- 

 .";-• tremity of this and other kinds of gonophore 



*> o^ usually becomes narrowed into a short stalk of 

 le ^l)^ attachment. Such a form of the reproductive 



bud is of comparatively rare occurrence. Ex- 

 1 thet amples may, however, be found in some species of 



s Eydractinia, Coryne, and Clava. 

 e g^ To understand the structural modifications of 



a 



to trace briefly the principal phenomena which 

 the more complex of these bodies present in the 

 course of their development, 

 g. All gonophores first appear as simple processes 



of some portion of the body-wall, with its two 

 layers, the ectoderm and endoderm. Next, the 

 ^H process becomes better defined, and exhibits 

 J » & peduncle or stalk. " When this process has at- 

 modi::'.: tained a certain size, its distal wall becomes 

 u D thickened, and projects as a sort of rounded boss 



into the cavity, which, in consequence, becomes 

 v h cup-shaped. As the process enlarges, the upper 

 I from ■ P art 0I> the cup-shaped cavity extends between the 

 Dtenr rounded central boss and the outer wall, under the 



form of four canals, which run up parallel with 

 the axis of the process, but stop short of its ex- 

 tremity. Their caecal ends then send out lateral 

 processes, so as to become T shaped, and ulti- 

 mately the lateral processes unite together, so as 



^3 t0 give lise t0 a circular canal uniting the ends of 

 r m ( the four longitudinal canals. Contemporaneously 

 ie 01 •• with these changes, the axis of the boss becomes 



hollowed out by a canal continuous with the 



original cavity of the process, and like it lined by 



ody* the endoderm. A separation now takes place be- 



