THE AMERICAN LOBSTER. 
49 
taken from the well of a fishing- smack, after extrusion had been partially accomplished, 
at Rockland, Maine, August 6, 1893. The lobster, I was told, was taken out and laid 
on the deck, when the soft, dark-green mass of eggs began to flow away from the body 
from their own weight. (Compare note 1, p. 47.) 
Cano (32) gives the following detailed account of the laying of the eggs in the 
crab Maia: 
The time that intervenes between copulation and the deposit of the eggs may be eight, ten, fifteen 
days, or even longer, and can not be fixed, since copulation happens before the eggs mature in the 
ovary. The eggs, at the time of ovulation, pass the opening of the receptaculum seminis, and are here 
invested with a coat of cement, which is secreted and held in the receptacle. The eggs then revolve 
on their axes m the vaginal canal, and are expelled, one at a time, by means of the valvular apparatus. 
This is formed by a prolapsus of the vaginal canal. * * Besides the proper muscles of this canal 
there exist special muscles which, by lowering the membranous covering, provoke the expulsion of 
the eggs through the valvular orifice. The eggs thus ejected fall into the abdominal chamber. The 
female heats them about with repeated blows of the tail, while the pleopods, keeping them in 
continued agitation, make them converge toward the center of the abdominal pouch. The deposition 
of eggs is effected in Maia in the course of twenty-four hours, but sometimes in Lissa it takes a longer 
time. On the next day all the eggs adhere in groups, by means of one or two peduncles, to the hairs 
of the internal branches of the pleopods, while the external branch agitates them continuously. 
This movement, besides renewing the surrounding water, probably assists in rupturing the egg shell, 
when the embryos are ready to hatch. Fixation could not be explained without the interaction of 
the sea water. The cement at first becomes more viscous, then hardens and forms a very thin pellicle, 
which, with the growth of the embryo, becomes quite hard and resistant. It would seem that the sea 
-water might explain the chemical change which the cement undergoes, a change analogous to that 
which is observed in the exoskeleton after the molt. The cement may he regarded as a substance 
very like chitin, both being of ectodermic origin. The cement serves not only for fixation, hut 
unquestionably as the vehicle of the seminal elements toward the eggs. 
If we examine the zone of cement which invests the eggs at the moment the latter traverse the 
short vaginal canal, there is seen a large quantity of seminal corpuscles, some of these still in the 
spermatophoral envelope, others free and swimming in the homogeneous mucus. These vary both in 
shape and dimensions. All the elements are immobile, hut once I noticed that some of these cells, 
especially those with radial prolongations, were endowed with amoeboid movements. Whether these 
movements are the same as those which impel the sperm into the egg I can not say from direct observa- 
tion. The question then remains open as to when and how the spermatozoa pass into the eggs, which are 
unprovided with a micropyle. If they are able to penetrate through the poral canals of the chorion, 
and if this penetration can happen during the very brief passage of the egg through the vaginal 
canal or at the moment of deposition of the eggs, as in the Macrura, then the sea water must exert 
unknown physico-chemical actions on the cement, which makes the egg itself adhere later to the hairs 
of the pleopods. 
The typical phenomena of fecundation — the expulsion of the polar bodies and formation of 
pronuclei — I have not been able to observe directly. 
When the eggs have reached the receptaculum seminis the nucleus has become invisible. The 
first segmentation nuclei are found in the central part of the eggs and move toward the periphery. 
Segmentation begins almost as soon as the eggs are fixed. 
Cano (33) observed cases in Carciuus and Portunus where the eggs were laid at 
different periods, one-third of the eggs being in the morula stage and the rest ready 
to hatch. Again, it was rarely found that the eggs were laid just before the molt, in 
which case they were cast off and destroyed. This anomalous condition was first 
noticed by Lo Bianco in Palinurus (18). 
F. C. B. 1805—4 
