Mr. J. D. Macdonald on Phyllirrhoe buccpliala. 459 



towards the auricle, bringing back the aerated blood from the hinder 

 extremity of the hody. There are no visible respiratory organs, but 

 it is probable that the cutaneous surface permits of the necessary 

 exposure of the blood to the air contained in the surrounding 

 medium. 



The nervous system is well developed. The supra- and subceso- 

 phageal ganglia, with their commissural chords, form a close ring 

 round the gullet immediately behind the buccal mass. The audi- 

 tory sacs, which are filled with vibratory otokonia. appear to lie be- 

 tween both sets of ganglia, and the rudimentary visual organs, con- 

 sisting each of a simple cell containing a refracting globule imbedded 

 in black pigment, are also in contact with the nervous matter. Be- 

 sides the actual distribution of the nerves given ciF from the cephalic 

 ganglia, I noticed nodules of neurine lying at the base of the tenta- 

 cula, communicating by commissural threads, and sending off each 

 a principal nerve to the corre.-ponding tentacle. The ganglion- 

 globules were lined with a reddish-coloured pigment, deposited 

 round the vesicular nuclei, and when twigs are given off from the 

 smaller nerves, both the homogeneous neurilemma and the contained 

 nervous matter break up like a dividing vessel, without preserving 

 the individuality of distinct nerve-tubes. 



The sexes are combined in Phyllirrhoe, the male and female 

 generative openings lying close together on the right side of the 

 body in the inferior gastero-hepatic space, and before the anal aper- 

 ture. The ovaries lie in the inferior recto- hepatic space, varying in 

 number from two to five, in general. They are dark- coloured, sub- 

 rotund, and finely lobulated bodies, from the fore part of each of 

 which a very delicate duct arises, and all the ducts unite to form a 

 single tube, with a trifling increase in its diameter. This common 

 oviduct, lined by a pavement of transparent epithelial cells, passes for- 

 wards beneath the stomach in a flexuous manner ; and in the inferior 

 gastero-hepatic space, it first unites with the duct of the testis and 

 again continues its devious course until it ends in the fundus of a 

 much larger tube, whose lining membrane is armed with numerous 

 conical and tooth-like processes, and to this is appended a long csccal 

 process much resembling the spermatheca of Helix for example. 

 The external orifice of the male generative apparatus lies immedi- 

 ately posterior to that of the female organs. The testis is rather 

 small, subglobular in form, and closely connected with a short 

 twisted tube*, much dilated at the middle part, and coated over with' 

 a layer of dark ])igment-cells. It is with this tube, as above noticed,' 

 the small oviduct communicates, in order, as it would seem, to permit 

 of self-impregnation, or to answer some other purpose, with the na- 

 ture of which we are unacquainted ; but there is also an intromit- 

 tent organ, which, however, I have never seen proi)erly exserted. 



As to the afl&nities of Phyllirrhoe with Gasteropods, it may be ob- 



* I have distinctly traced the homologue of this tube in Pteropoda, Heteropoda, 

 and the Gasteropoda proper. 



30* 



