376 Transactions of the Societn. 



tlie fertilization of two or more depositions of ova, the sperma- 

 tozoa being retained by the female in a " rcccptacuhun seminalis," 

 and the ova fertilized from this supply at the time of de- 

 position. I have not had an opportunity of observing the act of 

 copulation in Portunus, but one may suppose tliat in all probability 

 it takes place very shortly after the female crab has moulted, and 

 before her shelly armour has had time to harden. That certainly 

 appears to be the case as regards the Common Shore Crab (Carcinus 

 mayiias), and the remarkable little Maslved Crab {Gorystes cassive- 

 launus), which on several occasions I have watched on the wide 

 sandy shores of Dymchurch Bay. 



This interesting phenomenon of repeated depositions of fertile 

 ova, as the result of one impregnation Ijy the male crab, has also 

 been observed by my friend, Mr. H. J. Waddington, of Bourne- 

 mouth, whose beautiful preparations of marine and fresh-water 

 organisms have frequently been exhibited at the Meetings of this 

 Society. Last year, when very kindly sending me a beautiful 

 slide of the ova of Portnnus, Mr. Waddington at the same time 

 furnished me with a very interesting account of his own observa- 

 tions on the subject, which confirmed in all points my own ex- 

 perience. Mr. Waddington, in his letter to me, also states that he 

 referred the matter to Dr. H. C. Williamson, of the Fishery Board 

 of Scotland, who was able to confirm the fact that one impregnation 

 of the female crab is sufficient for the fertilization of two or three 

 depositions of ova. 



In illustration of this interesting phenomena, I have pleasure 

 in showing to-night under the Microscope the preparation of ova 

 from a second deposition sent me by Mr. Waddington, and a series 

 of photomicrographs which I have made from my own material. 



