cavity. The sexes are generally but not always similar externally, and may be distinguished on dissection by the difference between the sperm-cells and the ova. The ovary w

horus helleri Heckel. The anal fin modif

individuals. Usually there are no external genital organs, but in some species a papilla or tube is developed at the end of the urogenital sinus. This may exist in the breeding season only, as in th

a number of families the species are ovoviviparous, the eggs being hatched in the ovary or in a dilated part of the oviduct, the latter resembling a real uterus. In some sharks there is a structure analogous to the placenta of higher animals, but not of the same structure or origin. In the case of viviparous fishes actual copulation takes place and there is usually a modification of some organ to effect transf

rous, with young, Cymatogaster a

fishes (Sebastodes) and rosefishes (Sebas

. A viviparous fish from Lake Patzcuaro,

number. In the viviparous sharks, which constitute the majority of the species of

tarcticus, the Bottle-nosed Chim

ks (Heterodontus) are spirally twisted, those of the cat-sharks (Scyliorhinid?) are quadrate with long filaments at the angles. Those of rays are wheelbarrow-shaped with four "handles." One egg-case of a ray may sometimes contain

ine limosa Girard, showing threa

0,000 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

rk, Heterodontus philippi (Lacép

h 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, Conorhynchos) the male carries the eggs in his mouth, thus protecting them from the attacks of oth

) the female is said to deposit her e

lue, red, black, and silvery-white pigment are especially characteristic of the male, the olivaceous and mottled coloration of the female. Sometimes the male h

aja) the pectoral fin has near its edge two rows of stout incurved spines. These the female lacks. In the breeding season, among certain fishes, the male sometimes becomes much brighter by the accumulation of bright red or blue pigment accompanied by black or white pigment cells. This is es

eason, the jaws and teeth being greatly elongated and hooked or twisted so that the fish cannot shut its m

permanent, nor is there anything to be called personal

ning-grounds without much reference to the preference of the females. In general the brightest colors are not found among viviparous fishes. None of the groups in which t