158 Miscellaneous. 
MISCELLANEOUS. 
Cement-glands and Origin of Egg-membranes in the Lobster. 
By Francis H. Herricx, of Adelbert College. 
Tur cement-glands have hitherto escaped detection in the lobster 
(Homarus americanus), and consequently the origin of the gluey 
secretion in which the eggs are immersed at the time they are laid, 
and by means of which they are attached to the body, has never 
been accurately determined. 
Cano’s valuable studies (“ Morfologia dell’ appareccio sessuale 
feminile, glandole del cemento e fecondazione nei Crostacei Decapodi,” 
Mittheil. Neapel, Bd. ix.) have called attention to the much-neglected 
cement-glands of the Decapod Crustacea. 
Erdl, in 1848, described three egg-membranes in the egg of the 
lobster, and regarded the outermost of these as a secretion-product 
of the oviduct. Bumpus also (‘Journal of Morphology,’ vol. v- 
no. 2) attributes the “varnish-like layer,” which surrounds the 
ovum of Homarus at the time of oviposition, to a secretion which 
probably comes from the columnar cells of the oviduct. Lereboullet 
just escaped the discovery of the cement-glands in 1860, but cor- 
rectly stated that the cement-substance came from beneath the skin 
of the underside of the abdomen. The true cause of this secretion 
was first recognized by Braun in 1875, and the subject has been 
recently investigated in a large number of Decapods with great 
clearness by Cano. 
When the lobster-embryo is about to hatch it is invested by three 
membranes, from which it escapes to enter upon its first free- 
swimming larval stage. The outermost of these is the membrane of 
attachment. Within this is the chorion, which is now nearly 
absorbed. This is exceedingly delicate, and is often carried away 
with the former in the process of hatching. The innermost mem- 
brane does not belong to the egg, but to the embryo, which it closely 
invests. The casting-off of this membrane forms the first moult, 
and unless it is successfully thrown off the larva dies. The earlier 
embryonic cuticles, which are formed in the long course of embryonic 
life, are entirely absorbed at the time of hatching. 
The secondary egg-membrane, or membrane of attachment, com- 
pletely separates from the chorion at the time of hatching, except 
at one point, which is often opposite the thread-like stalk, with 
which the outer capsule of the egg is continuous. The outer mem- 
brane, which is less elastic than the chorion, is subjected to a high 
degree of tension, until it finally bursts, splitting into two symme- 
trical halves along the vertical longitudinal plane of the body of the 
embryo, beginning at the hinder end and coming off over the head 
and tip of the abdomen. 
When the chorion or primary egg-membrane is removed from the 
