In some viviparous fishes, as in the rockfishes (Sebastodes) and rosefishes (Sebastes), the young are very minute at birth.
Fig. 93.—Goodea luitpoldi (Steindachner). A viviparous fish from Lake Patzcuaro, Mexico. Family Pæciliidæ. (After Meek.)
In others, as the surf-fishes (Embiotocidæ), they are relatively large and few in number. In the viviparous sharks, which constitute the majority of the species of living sharks, the young are large at birth and prepared to take care of themselves.
Fig. 94.—Egg of Callorhynchus antarcticus, the Bottle-nosed Chimæra. (After Parker and Haswell.)
The eggs of fishes vary very much in size and form. In those sharks and rays which lay eggs the ova are deposited in a horny egg-case, in color and texture suggesting the kelp in which they are laid. The eggs of the bullhead sharks (Heterodontus) are spirally twisted, those of the cat-sharks (Scyliorhinidæ) 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 several eggs and develop several young. The eggs of lancelets are small, but those of the hagfishes are large, ovate, with fibres at each side, each with a triple hook at tip. The chimæra has also large egg-cases, oblong in form.
Fig. 95.—Egg of the Hagfish, Myxine limosa Girard, showing threads for attachment. (After Dean.)