MUSEUM OF COMPARATIVE ZOOLOGY. 173 



had originated there. The dorsal sac was moderately large, and con- 

 tained numerous spermatozoa, which were, however, scattered, and not 

 in groups. I do not know how to explain this case, unless indeed it be 

 due to a rupture of the dorsal sac in places, and the consequent evacua- 

 tion into the body cavity of a part of its contents. Although I did not 

 find any point at which this could be shown to be unmistakably true, 

 yet there were many places where the wall could not be distinguished ; 

 furthermore thie body was in this case much distorted in killing. Even 

 when the outlines of the sac are plainest, one always finds spermatozoa 

 in the body cavity in greater or less numbers ; so, for example, in the 

 cavity of the terminal organ (Plate IV. Fig. 53.-). This, so far as I 

 know, is the only fact which favors the view that their place of origin 

 is in the body cavity ; aside from this, the evidence points to the dorsal 

 sac as testis. A further study of additional material is necessary to 

 determine finally this point, as well as many others. 



The external sexual organ of the male consists of the terminal pa- 

 pilla to which reference has often been made. It has much the shape 

 of a slightly curved truncated cone (Fig. 53) with an opening at the 

 smaller base, and with the larger base joined to the body obliquely, so 

 that it naturally turns ventrad. The length and curvature of the organ 

 vary a little, as can be seen from the different figures (Figs. 4, 9, 53, 89, 

 90). The essential features of its structure can be made out from a total 

 preparation in clove oil (Fig. 53). The muscular layer of the body wall, 

 which for some distance has been growing thinner, stops suddenly along 

 a well defined line. Beyond this only the hypodermis lies between the 

 cuticula and the body cavity. The cuticula, which is here a little thicker 

 than usual (see also Plate VII. Fig. 90) is infolded at the end of the or- 

 gan and runs forward as the lining of the cavity for a variable distance. 

 I was at first inclined to believe that this infolded portion could be to a 

 limited extent extruded and then drawn in ; but further study seems 

 to show that it cannot. The thick cuticula is too stiff to be rolled in 

 or out without being folded somewhere, yet on sections it is always 

 smooth ; moreover, there is no muscular provision for moving the organ 

 in this way. At its anterior end the cuticular infolding is continous 

 with a sac (va. elf.) having delicate walls, and this is in turn connected 

 with the dorsal sac previously described (Fig. 53 and Plate VI. Fig. 89, 

 va. (If.). Although I plainly saw and dr*ew in several cases the walls of 

 this connecting portion from clove oil preparations, yet they are so deli- 

 cate that in sections they were not once preserved except as loose shreds 

 of tissue. I was consequently unable to ascertain whether there was 



