REPORT ON THE CRUSTACEA MACRURA. 447 



variance from the observations of preceding writers, and the greater advantages at his 

 disposal in the quantity of living specimens at his command. 



Those in the Challenger collection, although numerous and obtained from all parts 

 of the Atlantic and Pacific Oceans within tropical and subtropical regions, are few in 

 comparison, especially those in which the reproductive parts in either sex are in a conditiou 

 for analytical examination, and these from their long retention in an alcoholic fluid, are 

 less transparent than those that were at the command of Professor Brooks. 



In our male specimens the testes are numerous and suspended in bunches from a 

 continuous cord apparently traversing the median line immediately beneath the 

 alimentary canal, extending anteriorly as far as the second pair of gnathopoda, and 

 posteriorly to the first somite of the pleon, where it appears to me to be connected with 

 a large chamber that extends posteriorly in the form of a gradually narrowing and 

 pointed cul de sac, in which the spermatophores are developed, and from the anterior 

 extremity of this cavity an opening on each side anteriorly passes into a vas deferens that 

 descends almost vertically, or at most but slightly forwards to the posterior ventral ex- 

 tremity of the pereion, one on each side of the neural cord that traverses the ventral 

 surface of the pereion. It is probable that in the same animal only one duct is in use, 

 inasmuch as two spermatophores are never equally developed at one time or proceed 

 simultaneously, and when they succeed each other with rapidity, they, according to the 

 figures given by Dana and Professor Brooks, traverse the same channel in succession. 

 Undoubtedly in the specimens that I have studied, the vas deferens sometimes passes 

 down on the left side, as shown on PI. LXXX. fig. 1, while in another specimen it is 

 on the right side ; in the latter the vas deferens appears to be empty, as if a spermato- 

 phore had recently been extruded, whde the nuclei of three others appear to be in a state 

 of formation. In the former specimen a spermatophore appears to be approaching the 

 period of extrusion, and another in an earlier condition within the chamber. 



The spermatophore when ready to be discharged is quite equal to, and in some 

 instances longer than, half the depth of the animal, the large end in advance, the sharp 

 or pointed extremity following ; when the stouter end reaches the external extremity 

 of the passage through which it travels, it presses against a thin membrane that appears 

 to close the orifice of the vas deferens and retain the spermatophore in position until 

 circumstances require its extrusion ; it is then in all likebhood caught by the petasma, 

 where it is retained untd it is required for the impregnation of the ovum. 



That the petasma is capable of so holding it may, I think, be accepted from an 

 examination of its structure, which I have illustrated on PL LXXX., ptm, showing it in 

 lateral aspect, with the anterior central portion, which is considerably advanced, detached 

 and more highly magnified to show the inner surface corrugated in the median line as if 

 it were formed for grasping and holding the spermatophore, which it probably does, by 

 the latter being dropped with the thick end into the grasping process of the petasma, the 



