INTRODUCTION. xli 



organs, which have previously escaped the observation of 

 anatomists, the author says, " are very irregular sacs, 

 variable in form, simple or compound ; they are generally 

 about three-quarters of a millimetre in length, but some- 

 times less. They are situated deeply on each side the 

 stomach, and are retained in their position by delicate 

 but strong ligaments, which are covered with black pig- 

 ment, which lose themselves between the muscular fascise 

 of the segments of the body. These organs are full of 

 cells, that M. Lereboullet considers as the spermatic 

 cellules. The second vesicles, or those which we thought 

 to be the true testes, M. Lereboullet calls testicules acces- 

 soires. Thev are, he savs, three in number on each. 



*' V * 



enlarged towards the middle ; they thin out insensibly 

 towards the extremities : at one end they unite with the 

 organs that M. Lereboullet calls the testes, and at the 

 other they open into the spermatic reservoir the vesicula 

 seminalis. These accessory testes contain cells which are 

 of two kinds, the larger being less numerous than the 

 others. From these vesicles an efferent duct leads to the 

 vesicula seminalis, which in Ligia is a long and narrow 

 vessel, increasing in breadth gradually as it approaches its 

 extremity, where it is suddenly constricted to a narrow 

 outlet, which, covered with black pigment cells, leads 

 direct to the external penis, which is situated near the 

 centre of the ventral arch of the seventh segment of the 

 pereion. In the males, processes of the branchial appen- 

 dages are developed into stylets, (vide fig. 12), that we 

 suppose must have some secondary influence in the pro- 

 cess of fertilization. 



The anatomy of the reproductive organs in the females 

 has been carefully worked out by MM. Loven and Bru- 

 zelius in the Amphipoda, and by Lereboullet and Schobl 

 in the Isopoda. 



