44 HYDROZOA. 



of rough weather usually disappear, their func- 

 tion having been, in all probability, previously 

 discharged. Yet nothing can be more perfect 

 than the series of transitional forms which estab- 

 lish the connection between these highly differen- 

 tiated organisms and the simple reproductive ap- 

 paratus occurring in Hydra. A few gradations 

 may be indicated. Thus, the closed gonophore of 

 Cordylophora sends off from its manubrial cavity 



em 



with true gonocalycine canals (fig. 8, g). In 

 Titbularia indivisa, fully developed canals are 

 exhibited by a distinct gonocalyx, but this never 

 becomes detached {fig. 9). Neither does it pre- 

 sent marginal tentacles, though even these sur- 

 round the fixed gonocalyces of Campanularia Lb- 

 veni {fig. 10). And so we at once pass to the free 

 swimming generative cups of other Hydrozoa. 

 But it would be easy to dwell on further modifica- 

 tions. Plumularia pinnata, for example, has its 

 manubrium irregularly lobed, the lobes being, in 

 all probability, as Professor Allman suggests, in- 

 cipient gonocalycine canals, while in Campanvr 

 laria caliculata canals exist, though the manu- 

 brium itself is suppressed. And in some gonophores, 

 the canal system, at first easily recognisable, be- 

 comes obliterated by age. 



A 



may 



velopment four distinguishable stages, which cor- 

 respond, respectively, to the permanent forms of 

 the reproductive body in particular members of 

 the group. These conditions are : — 



That of a simple expansion of the body-wall 



Hyd 







