Anatomy and Affinities of Ilypsobia nosoplioia. 409 



The abdominal ganglion is situated between the anterior 

 end of the kidney and the columellar mu-!cle. 



The cerebral ganglia give off anteriorly ocular, tentacular, 

 and labial nerves, and connectives to the buccal ganglia. 



It would appear that the penis-nerve is of cerebral origin, 

 though it is impossible to make absolutely certain of this. It 

 is possible that the tentacular nerve supplies branches to the 

 niuscuhvture of the eye. 



Each of the pedal ganglia gives off three main nerves, the 

 two anterior ones bearing small ganglia at a short distance 

 from their roots. These ganglia in their turn give off each 

 two nerves wliich apparently innervate the plantar muscu- 

 lature of the foot. 



VI. Reproductive System. 

 Male Organs. 



The spermatozoa have long and tapering heads, dlffi'riiig 

 therein from iho^Q oi Faludestrina (li) and Bythinella (2) , 

 and agreeing rather with P. taylori {sc. = Aninicola) (Ivob- 

 son MS.). Whether they possess the extraordinarily long- 

 tail seen in the latter is, however, doubtful. 



The vas deferens, after quitting the region of the testis, 

 becomes progressively more slender. It passes into the 

 prostate, which is of considerable size, and on quitting the 

 latter it passes over the floor of the mantle-cavity and up the 

 penis surrounded by a thick layer of circular muscle. 



The prostate is very much folded. The cells lining its 

 cavity are sparsely ciliated. It is difficult to be very certain 

 about the histological elements composing this gland. In 

 the first place, it usually showed differential staining, certain 

 areas being more darkly stained than others. But it is 

 impossible to say whether this was due to the presence of 

 different types of cells or different physiological states of a 

 single type of cell. It was possible to distinguish (a) vacuo- 

 lated cells with the nucleus somewhat flattened out and found 

 very often at the interior end of the cell (the end next the 

 lumen of the gland), and [U) cells with eosinophilous granular 

 cytoplasm, with the nucleus more usually rounded and occu- 

 pying a more median ])osition. 



The penis is undivided, agreeing therefore with Paludestrina, 

 Ilemilria, Delavaya, Stenothyra, and Tricida, and differing 

 from the Bythiniinse (l). It is cephalic in position. In all 

 the examples dissected it was rather broader and stouter than 

 that figured for ii. humida by Ileude (5). 



