THE LEECHES OF MINNESOTA 47 



somatic nerves, while the distal end of the packet lies some distance 

 out on the anterior (dorsal) side of the nerve. The anterior lateral 

 packets occupy a position antero-dorsal to the posterior packets 

 against which they are closely crowded. The left posterior lateral 

 packet of ganglion XXIX has been completely divided by the nerve 

 so that half comes to lie on either side of it; both parts, however, 

 enter the common fibre tract at the same place (PI. E, Fig. 21). The 

 lateral packets of somite XXXIV have been crowded entirely away 

 from their lateral position so that they have come to occupy a central 

 position, close together upon the dorsal side of the ganglion. Along 

 the median line of the fibrous portion of the mass is to be seen the line 

 of openings which are the remains of the commissural openings. They 

 are six in number, separating the seven ganglia of the mass, and in the 

 center of each is to be seen the very short piece of the Nerve of Faivre. 

 At either side of these openings are the usual central glia cells. 



Eyes. 



There is a single pair of eyes situated near together at III/IV. 

 The pigment cup and visual cells are deeply seated and the sensory 

 cells from the sensillae (sensilla III) are correspondingly long. I 

 find nothing in my sections of young leeches to< suggest the doubling 

 of the eye as found by Whitman, '92, for Clepsinc hollensis. There 

 are a few pigment cells below sensilla II and a similar group below 

 sensilla IV, but there is no arrangement of them which would indi- 

 cate an optic cup containing visual cells. 



Reproductive Organs. 



(PI. C, Figs. 3 and 4, and PI. D, Figs. 11 to 16.) 



The male genital pore, ( $ , Fig. 3, PL C and Fig. 11, PI. D) 

 lies in a mid-ventral position at XI/XII. The female genital pore, 

 ( 2 , Fig. 3, PI. C and Fig. 11 and Fig. 16, PI. D) lies two rings be- 

 hind the male opening at XII 2a/ ja. There are six pairs of testes, 

 (T. Fig. 4, PL C and Figs. 11 and 12, PL D) situated inter-segmen- 

 tally from XIII/XIV to XVIII/XIX. They are nearly spherical 

 in shape and lie in the spaces between the crop diverticula, the 

 last pair lying behind and median to the last pair of diverticula. 

 Owing to the pressure of the other organs they are somewhat flat- 

 tened antero-posteriorly with the exception of the last pair which 

 are larger than the others, and, as they have no diverticulum be- 

 hind them, are considerably elongated. 



