1908.] ASPIDOBRA>fCH GASTROPOD MOLLUSCS. 821 



show, is in fact in front of the suspensory membrane of the 

 ctenidium, close behind the thickened margin of the left side of 

 the mantle and in front of the anterior end of the left cokimellar 

 muscle. Close below the osphradium is a complex of ill-defined 

 ganglionic enlargements, and as Boutan failed to find the true 

 osphradium he missed the ganglia lying beneath it. In this 

 same paper Boutan argues, erroneously as I now think, that the 

 so-called subintestinal ganglion of Bouvier is not a member of 

 the group of visceral ganglia and gives figures of the pleuro-pedal 

 ganglia of Kerita and Sejitaria correcting the older figures of the 

 latter author. 



In the following year Bela Haller (20), in the course of his 

 studies on docoglossate and rhipidoglossate Prosobranchs, gave a 

 tolerably full account, not only of the nervous system, but also 

 of the alimentary tract, kidneys, and genital organs of Nerita 

 ornata. This work contains a curious mixture of acute and 

 accurate observations and incomprehensible errors and omissions. 

 His elaborate figure of the nervous system is in some respects 

 the best that has been published, but in other respects is most 

 misleading. As has already been mentioned, he flatly denies the 

 existence of a labial commissure, which is not only certainly 

 present, but much easier to dissect than in any other Rhipido- 

 glossate. I can positively assert that the numerous pedal 

 commissures figured by Bela Haller are not present : Bouvier 

 was perfectly correct on this point. In a simple dissection, one 

 may easily make mistakes in attempting to trace delicate nerves 

 through the mass of muscle in which they are embedded, but a 

 study of microscopical sections leaves no room for eri'or. A 

 careful examination of a series of sections of several species fails 

 to reveal any trace of transversal commissures posterior to the 

 main pedal commissure. B. Haller discovered the supra- 

 intestinal nerve, independently it seems of Boutan and Bouvier, 

 and gives a fairly correct figin-e of the crossed visceral commissure. 

 Like Boutan he identifies the elongated ganglion on the right of 

 the crossed visceral commissui^e as the subintestinal, but he did 

 not see the stout nerve given oW from it, almost immediately 

 swelling up to form the genital ganglion lying on the oviduct or 

 sperm-duct. In respect of the supra-intestinal and branchial or 

 osphradial ganglia, Haller gives a complicated figure which, as 

 far as I am able to reconstruct these ganglia from serial sections, 

 may be correct, but after many attempts I have been unable by 

 simple dissection to verify his account. These ganglia are covered 

 by the thickened and folded epithelium of the osphradium, which 

 in all the species at my disposal is too opaque to allow the 

 gaiiglia to be seen by transparency. 



Haller's description of the alimentary tract is much more 

 accvirate than that of his predecessors. He gives a good account 

 of the position and general relations of the stomach, cesophagus, 

 and course of the intestine, but his observations on the buccal 

 bulb, salivary glands, &c. seem to nie defective. He describes 



