NATURAL HISTORY OF AMERICAN LOBSTER. 
309 
by a flattened membrane with double walls, representing the expanded capsule which 
surrounds the egg. In most cases the hairs furnish support to but a small part of the 
egg mass, the individual eggs being freely united with their neighbors. Thus in the 
prawn Eucyphotes, according to Coutiere, the capsular cement gives off three or four 
flattened bands, each of which is soldered at its apex to similar strands from other 
eggs. The point of union is marked in each band by a lozenge-shaped or circular thick- 
ening. This would indicate that the eggs are surrounded by a layer of the viscous 
cement, and separated by seawater until they come together. Each lozenge-shaped 
thickening would then represent the original points of contact of egg with egg, the 
strands being spun from the sheath by a mutual pulling strain, due to the weight of the 
moving eggs. 
This condition is especially interesting since it seems to prove that such eggs must 
have received their coat of cement before leaving the body. Unless it should appear, 
however, that the marks of contact may be completely effaced by fusion of the united 
strands, it offers no basis for a general conclusion regarding the origin of the cement 
substance in other decapod Crustacea, like the lobster and crayfish. It is probable that 
in this as in many other particulars there is no absolute uniformity. 
A much more anomalous method of fixation of the egg to the swimmeret is described 
by Williamson ( 281 ) for the crab, Cancer pagurus, and in Brachyura generally. Accord- 
ing to this observer, the eggs lie thick upon the hairs of the inner branches of the swim- 
merets, and are attached by independent and often intertwined stalks, but there is no 
union of egg to egg, as in Synalpheus, Homarus, and other Macrura. The eggs are 
attached to single hairs, which garnish the endopodites, and usually to hairs only. 
There are said to be two membranes in either ovarian or attached egg, namely, a delicate 
vitelline membrane and a chitinous chorion. Between these a slight perivitelline space 
is formed upon contact with sea water. How does it happen that the eggs escape the 
hairs of the exopodite, and how are they suspended to the silken hairs of the endopodite 
without a single case of adhesion of egg to egg, and with little sticking of hair to hair? 
Williamson in brief offers tlris explanation: “The intimate relationship between 
the egg and the hair is due to the hair acting as a skewer, upon which the eggs are impaled 
and strung.” Further, the hairs are supposed to penetrate the chorion and pass through 
a perivitelline space without injury to the vitelline membrane. The chorion thus pierced 
collapses, and a little albuminous perivitelline fluid is pressed out, which becomes adhe- 
sive in sea water and serves to glue the chorion to the vitelline membrane and the egg 
to the hair; later the glue and chorion is pulled out into the sheets or cords by which 
the egg is anchored to the hair. 
The solution of the problem of fixation in the eggs of the blue crab appears to 
carry us into deeper water than before. In order to make comparisons I have 
examined the eggs and abdominal appendages of the blue crab, Callmectes 
hastatus. Callinectes lays upward of 4,500,000 eggs,® and the endopodites of the 
swimmerets are buried out of sight by the mass. As in Carcinus these myriads of 
a Smith, S. I.: Report on the decapod Crustacea of the Albatross dredgings. Report of the Commissioner of Fish and Fish- 
eries for 1885, p. 618-619. Washington, 1886. 
