114 



HYDEOZOA. 



the progeny of the Hydriform polyps, during one phasis of their develop- 

 ment, were strictly medusoid in their form and organization ; and in 

 like manner it is now incontrovertibly established that the Acalephce 

 are, at a certain stage of their growth, to all intents and purposes 

 Hydriform polyps, as will be immediately evident. 



(295.) The Acalephs are now universally admitted to be bisexual ; 

 and the generative apparatus in both sexes is invariably found to be 

 more or less intimately in relation with the alimentary canal : that is to 

 say, as in the case of the polyps, the reproductive organs are append- 

 ages derived from the internal or nutritive system of the body. In 

 both the males and females of the great majority of genera, the testes 

 of the former and the ovaria of the latter are similarly disposed, and 

 present externally precisely the same structure, consisting of duplica- 

 tures of a delicate membrane, between which, in the case of the female, 

 ova are developed in great numbers, generally of a rich orange or purple 

 colour, so as to be conspicuously visible. In the male Acaleph, instead of 

 ova, the generative membrane secretes a vivifying fluid, rich in sperma- 

 tozoa, and consequently easily recognizable under the microscope. 



(296.) In Cyanea aurita the generative apparatus of the female con- 

 sists of four membranous ovaria, easily recognizable on account of their 

 bright colour, which is usually violet, or deep yellow. Their form 

 is generally semicircular 

 (fig. 53), and they are 

 lodged in as many distinct 

 cavities, situated in the 

 immediate vicinity of the 

 central stomachs. Each 

 of these cavities com- 

 municates freely with 

 the external element by 

 means of a large round 

 or oval orifice, furnished 

 internally with tentacula 

 having suckers at their 

 extremities (fig. 53, d.) 

 The four semicircular 

 ovaries are each com- 

 posed of a simple con- 

 torted tube (fig. 53, a, b) : 

 when full of eggs, its 

 colour is a beautiful vio- 

 let ; but when empty, or 

 when the ova are only 

 partially developed, a yellowish brown. 



(297.) The ova are not retained in the ovaria during the whole time 



1. Ovarium of Cyanea aurita. 



2. Ciliated embryo after its escape. 



