36 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 
with the latter class of fishes, those 
in which the eggs remain distinct, 
that artificial impregnation and 
Se aa hatching is practicable. In this re- 
Shark Heterodontus philippi gard the value of the salmon and 
(Lacépéede). (After Parker and trout is predominant. In some fishes, 
Haswell.) especially those of elongate form, as 
the needle-fish (Tylosurus), the ovary of but one side is 
developed. 
Protection of the Young.—In most fishes the parents take 
no care of their eggs or young. In some catfishes (Platystacus) 
the eggs adhere to the under surface 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 (Galeichthys) 
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 intruders, 
against the female as well as against outside enemies. The 
nest-building habit is especially developed in the sticklebacks 
(Gasterosteid@), a group in which the male fish, though a pygmy 
in size, is very fierce in disposition. 
