28 



The Organs of Reproduction 



outer walls. All contain food-yolk from which the embryo in 

 its earlier stages is fed. The eggs of the eel (Anguilla) are micro- 

 scopic. According to Gunther 25,000 

 eggs have been counted in the herring, 

 155,000 in the lumpfish, 3,500,000 in 

 the halibut, 635,200 in the sturgeon, 

 and 9,344,000 in the cod. Smaller 

 numbers are found in fishes with 

 large ova. The red salmon has 

 about 3500 eggs, the king salmon 

 about 5200. Where an oviduct is 

 present the eggs are often poured out 

 in glutinous masses, as in the bass. 

 When, as in the salmon, there is no 

 oviduct, the eggs lie separate and 

 do not cohere together. It is only 

 -^^ath the latter class of fishes, those 

 in which the eggs remain distinct, 

 that artificial impregnation and 

 hatching is practicable. In this re- 

 ,^, , r J . . , I,-,- ■ gard the value of the salmon and 



bnark, Heterodontus phdippi ° 



(Laci'pede). (After Parker and trout is predominant. In some fishes, 

 HaswcU.) especially those of elongate form, as 



the needle-fish (Tylositnis), the ovary of but one side is 

 developed. 



Protection of the Young. — In most fishes the parents take 

 no care of their eggs or j^oung. In some catfishes (Platystaciis) 

 the eggs adhere to the under surface of the female. In a kind 

 of pipefish (Solenostomns), a large pouch for retention of the eggs 

 is formed on the belly of the female. In the sea-horses and 

 pipefishes a pouch is formed in the skin, usually underneath 

 the tail of the male. Into this the eggs are thrust, and here the 

 young fishes hatch out, remaining until large enough to take 

 care of themselves. In certain sea catfishes {Galeiclitliys, Couo- 

 rhynchos) the male carries the eggs in his mouth, thus protecting 

 them from the attacks of other fishes. In numerous cases the 

 male constructs a rough nest, which he defends against all in- 

 truders, against the female as well as against outside enemies. 

 The nest-building habit is especially developed in the stickle- 



FlG 



Egg of Port Jackson 



