EGGS OF ELASMOBRANCHS 183 
be covered with a thin layer of sand or gravel, —the 
spawners always returning to the same nest, —and a sec- 
ond, third, and more tiers of eggs will be added. When 
the eggs have finally been deposited, the nest is fortified 
by a dome-like mass of pebbles and stones, which the lam- 
preys carefully drag to the spot. The nest is thus marked 
out as well as protected, and is said to be made of partial 
use during the following season. The hatching of the 
eggs takes place within about a fortnight. 
The eggs which Sharks and Rays deposit are usually 
enclosed in a stout, horn-like capsule; this is in general of 
oblong or rectangular outline, its surface smooth or ridged; 
the case of the egg of Scy/lium (Fig. 189), shows thread- 
like terminal processes, while these in the ray (Fig. 189 A) 
are stout and spine-like. A great variation may exist in 
the size of the egg and in the character of its envelopes 
among the different groups of Elasmobranchs. The egg 
of the Port Jackson shark, Cestracion (Fig. 190), is of enor- 
mous size and possesses an extremely thick, spiral-rimmed, 
pear-shaped capsule ; that of the Greenland shark, Lemar- 
gus, is said to be spherical and relatively small, and to be 
deposited unprotected by capsule. 
The breeding habits of Elasmobranchs are but imper- 
fectly known. With the exception, perhaps, of Lamargus, 
the sexes copulate.* The clasping appendages of the male 
_ are inserted either singly or together into the cloaca and 
oviduct of the female, and the eggs appear to be fertilized 
in the uppermost portion of the oviduct. The egg then 
becomes surrounded by a glairy albuminous envelope, and 
thereafter by the secretion of the oviducal gland, which in 
the lower oviduct hardens into the horny capsule. The 
* The copulation of sharks has been but rarely observed (¢,. by Bolau in 
Hamburg ; cf. Ref. on p. 241). 
