INTRODUCTION. xhi 
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 fasciz 
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 ¢esticules acces- 
soires. They are, he says, three in number on each, 
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 Jsopoda. 
