172 Instincts, Habits, and Adaptations 



supial pouch for the eggs or young is found in the males only, 

 and Gasterosteus, where the male constructs the nest and pro- 

 tects the eggs during incubation from the voracity of the females. 



" In some individuals the eggs had been recently laid, in 

 others they were hatched and the foetus had grown at the ex- 

 pense of some other food than that derived from the yolk, as 

 this- last was not proportionally diminished in size, and the 

 foetus weighed more than the undeveloped egg. The number 

 of eggs contained in the mouth was between twenty and thirty. 

 The mouth and branchial cavity were very much distended, 

 rounding out and distorting the whole hyoid and branchiostegal 

 region. Some of the eggs even partially protruded from the 

 mouth. The ova were not bruised or torn as if they had been 

 bitten or forcibly held by the teeth. In many instances the 

 foetuses were still alive, though the parent had been dead for 

 many hours. 



" No young or eggs were found in the stomach, although 

 the mouth was crammed to its fullest capacity. 



"The above observations apply to njinge-njinge. With re- 

 gard to jarra-bakka, I had but few opportunities for dissection, 

 but in several instances the same conditions of the eggs were 

 noticed as stated above; and in one instance, besides some 

 nearly mature foetuses contained in the mouth, two or three 

 were squeezed apparently from the stomach, but not bearing 

 any marks of violence or of the action of the gastric fluid. It 

 is probable that these found their way into that last cavity after 

 death, in consequence of the relaxation of the sphincter which 

 separates the cavities of the mouth and the stomach. These 

 facts lead to the conclusion that this is a mouth gestation, as 

 the eggs are found there in all stages of development, and even 

 for some time after they are hatched. 



"The question will be very naturally asked, how under such 

 circumstances these fishes are abie to secure and swallow their 

 food. I have made no observations bearing upon such a ques- 

 tion. Unless the food consists of very minute particles it would 

 seem necessary that during the time of feeding the eggs should 

 be disgorged. If this supposition be correct, it would give a 

 very probable explanation of the only fact which might be con- 

 sidered at variance with the conclusion stated above, viz., that 



