THE AMERICAN LOBSTER. 49 



taken from the well of a lishing smack, after extrusion had been partially accomplished, 

 at Rockland, Maine, August t>, 181)3. The lobster, 1 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 tb;it intervenes between copulation and the doposit of the eggs inay 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 reccptaculum 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 in 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 spocial 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 beats 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 be regarded as a substance 

 very like chitin, both being of ectodermic origin. The cement serves not only for fixation, but 

 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, but 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 Carcinus 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). 



!■'. C. B. 1895—1 



