r 
308 bulletin of the bureau of fisheries. 
granular, more deeply stained, oval in form, and are farther removed from the basement 
membrane. Furthermore, large vesicular cavities occur within or between the cells 
next the lumen of the glands, where products of nuclear degeneration are not wanting. 
It thus seems evident that the glandular epithelium of the oviducts pour an abundant 
secretion over the eggs when these are delivered into the abdominal pouch. According 
to the account of Scott quoted above, the eggs are viscous when they leave the ducts, 
become adherent in sea water, but soon lose this property. So far as I have been able 
to ascertain, eggs to all appearance ripe, which were taken directly from the ducts shortly 
after egg laying, were nonadherent and showed no trace of cement or a secondary egg 
membrane, but at this time the action of the glands had ceased. 
In the lobster with external eggs in segmentation, referred to above, the oviducts 
were beaded with ripe eggs, or as Duvernoy expressed it, stuffed like sausages, with eggs 
which failed of passage arranged in line, but they were not viscous at the time of exami- 
nation, and were surrounded by the chorion only. Assuming that the oviduct contributes 
to the formation of the cement, some other chemical products would seem to be needed 
to render this effective. These are possibly supplied by the secretions of the tegumental 
or “cement” glands of the swimmerets in the presence of sea water. At all events it 
would seem that there is poured into the pouch at the time the eggs pass into it an abun- 
dant milky or turbid secretion from these glands, which under the microscope is seen to 
be swarming with minute floating particles or spherules. A similar secretion occurs in 
the crayfish, which after the setting of the cement is found to cover her eggs in a sort 
of protective “apron,” as Andrews calls it, a sheet of grayish mucus or glair. When 
this is removed the eggs appear bright and fresh beneath it. This “apron” seems to be 
a residue of unused material, the presence of which may be needed not only to hold the 
eggs and sperm in the pouch but to take part in the production of the liquid hydraulic 
cement. 
COMPARISONS WITH THE OTHER CRUSTACEA. AND THEORIES OF FIXATION. 
In the lobster the glue forms a thin transparent sac about each egg (fig. 5, pi. xliv 
mb^), and the capsules of adjoining ova are united by short solid ribbons, or flattened 
strands of the same material. Similar bands adherent to the hairs and often coiled 
spirally about them hold the entire egg mass to the body. The cement is thus a con- 
tinuous sponge work, which is imitated in the manufacture of certain kinds of nut candy, 
where the kernels are stirred in the thick sirup and held immersed when it hardens. 
Coutiere ® describes a slightly different mode of fixation in the Alpheidae (Alpheus 
and Synalpheus ) , where the eggs or egg-groups adhere only to the stalk of the pleopods, 
and never to the fifth pair of swimmerets, nor to the abdomen directly. The supporting 
hairs are bunched at the two extremities of the basal stalk and are nonplumose, as in 
the lobster. 
Where the eggs are few in number, as in Synalpheus longicarpus, they are glued 
direct to the hairs, but where more numerous several hairs are cemented into a cable 
oCouti&re, H.: Les “Alpheidae,” Morphologic exteme et interne; Formes larvaires; Bionomie. Annales des Sciences 
naturelles, 8“ s6r., Zoologie, t. ix, p. i — iv, p. 428. 
