Fig. 79.—Egg of a Scyllium from Magelhan’s Straits (? Sc. chilense). Natural size.
Fig. 80.—Egg-shell of Cestracion philippi, half natural size, linear.
I. External view. II. Vertical section.
a, One spiral ridge; b, The other spiral ridge; c, Cavity for the ovum.
The ova of the oviparous Chondropterygians are large and few in number; they are successively impregnated, and the impregnation must take place before they are invested with a tough leathery envelope which would be impenetrable to the semen, that is, before they enter the uterus; therefore, copulation must take place in all these fishes. The form of the egg-shell differs in the various genera; generally (Fig. [79]) they are flattened, quadrangular, with each of the four corners produced, and frequently prolonged into long filaments which serve for the attachment of the ova to other fixed objects. In Notidanus the surfaces are crossed by numerous ridges. In Cestracion (Fig. [80]) the egg is pyriform, with two broad ridges or plates, wound edgewise round it, the two ridges forming five spires. The eggs of Callorhynchus (Fig. [81]) have received a protective resemblance to a broad-leaved fucus, forming a long depressed ellipse, with a plicated and fringed margin.
Fig. 81.—Egg of Callorhynchus antarcticus. a, Cavity for the embryo.