106 



Part III. — Twenty-second Annual Report 



This I find is not the case, with adult crabs at least. Each crab 

 which I have examined after it had cast, and before it had been in 

 contact with the male, was found to have a spermatheca resembling 

 in general that of a hard crab, i.e., it contained a quantity of sperms 

 and some amber-coloured solid. If a soft crab which has been with 

 the male, and is plugged, be dissected, no amber solid will be found 

 in the spermatheca, and there is usually a large quantity of sperms 

 with a large quantity of amber fluid. When does the crab get rid of 

 the old sperms and amber solid 1 The inner lining of the spermatheca, 

 although it does not come away during moulting, is nevertheless 

 very loosely attached, and I have drawn out the inner lining and the 

 contents of the spermatheca, along with the lining of the vagina, through 

 the vulva, in a dead hard crab. On casting only a very little of the inner 

 lining of the spermatheca is shed ; that is, the part round the mouth. 



J ust inside the spermatheca the lining thins out quickly. The mouth 

 of the spermatheca is surrounded by a sphincter muscle, ?nu. t fig. 38. 



The break between the lining of the vagina and that of the sperma- 

 theca takes place near the point where the thick layer of the vagina 

 thins down to that, of the spermatheca (fig. 38). In the newly cast crab, 

 moreover, there was no fluid in the spermatheca. The spermatheca of 

 the crab has a glandular secreting surface. It is probably the case that 

 the secretion of the fluid causes the loosening of the inner layer, and on 

 the introduction of the penis the amber solid and the old sperms may be 

 expelled with the outflow of fluid. The secretion of fluid in the sperma- 

 theca is possibly stimulated by the presence of the male. The vulvae are 

 always tightly closed except when they are kept opeu by the plugs. On 

 the introduction of the penis the fluid will flow out round it in the vagina 

 and will prevent the entrance of sea-water into the spermatheca. Vide 

 diagram, fig. 55. This fluid coagulates with sea- water, forming a whitish 

 precipitate. The plug in the vagina is of a hard fibrous structure and 

 of white colour. During the time the male and female are in conjunction, 

 a period of probably several days, the piston-action of the second penis 

 would transfer the sperms to the spermatheca. The crab, then, on casting 

 does not get rid of the remains of the old stock of sperms until it has 

 the opportunity of being impregnated afresh. 



Some experiments were made with certain crabs which cast during 

 1902, August 31st to October 15th, and the results are of interest. A 

 female, measuring 5| inches across, was put with the male crab as soon 

 as it was seen to have cast, and four days later pieces of plug were seen 

 projecting from the vulva?. Another measuring 5 inches was separate 

 from the male two days after, and at that time a plug projected from the 

 vulva. A female crab, measuring 6f inches across, was kept for four 

 days after casting. It was not in contact with a male crab. It was then 

 killed : no fluid was found in the spermatheca. Six days after casting 

 the soft crab which measured Gy 1 ^- inches across, and which had not been 

 in contact with a male crab, was dissected. The spermatheca contained 

 sperms and a row of hard amber-coloured solid. A small soft crab, viz. 

 4-L inches across, was put with a male crab. Twenty- four hours after, 

 no plugs were seen, but they were visible two days after the introduction 

 of the female. 



It is to be noted that while in the male crab the sperms are contained 

 in spermatophores, in the spermatheca the sperms are loose ; in very few 

 cases was a spermatophore seen. According to Duvernoy, sea-water 

 causes the spermatophores to burst. 



The extrusion of the spermatophores from the vas deferens is no doubt 

 aided or effected by the following circumstances. The vas deferens of 

 the hard male crab is usually in a swollen condition, and therefore the 



