IlITRODUCTIOU. 



In spite of the extensive researches iat© the spermato- 

 genesis of the Decapods, the use of the peculiar structures 

 found in the sperms of these animals is still an unsolved 

 prol)lem. This is due to the fact that the entrance of the 

 sperm into the egg has never "been reported. While studying 

 the hat its and structure of Menippe mercenaria, a large 

 edible crah found along the southern part of the Atlantic 

 coast of the United. States, I had the good fortune to obtain 

 material which shows the essential features of this process. 

 In order to show which parts of the seminal cell are involved 

 in the process of fertilization, the genesis of the sperm 

 and the formation of the pronucleus in the fertilization of 

 the egg, as well as the entrance of the sperm, are here de- 

 scribed. The history of the male cell from its origin in 

 the epithelium of the wall of a tubule of the testis to its 

 association with the female nucleus in the center of the egg, 

 is here presented. 



The study of the life-history of Menippe mercenaria, 

 which led to the discoveries presented in this paper, was 

 undertaken at the suggestion of Prof. E. A. Andrews, and at 

 every step in the progress of this work I have received his 

 kind advice and helpful criticism. I am also greatly indebt- 

 ed to the Hon. Geo. M. Bowers, United States Commissioner of 

 Fish and Fisheries, for the privilege of working in the 

 Marine Biological Laboratory at Beaufort, II. C., and for the 



