796 PROF. G. C. BOURNE ON THE 



into the mantle-cavity to the left side of the genital ducts. As 

 may be seen in figs. 16-20 (Pis. XXXII. & XXXIII.), it extends 

 far beyond the hind end of the genital ducts, accompanying the 

 rectum in its course, and lying to the right side of the kidney 

 at the hinder extremity of the visceral mass. In the section 

 depicted in tig. 20, which passes through the rectal coil at the 

 bottom of the hind end of the visceral mass, the hypobranchial 

 gland on the right side of the rectum appears to form a pair with 

 the kidney on the left, but there is, of course, no relationship 

 between the two organs. Throughout its course the hypobran- 

 chial gland con.sists of an iriegularly folded flattened sac, from 

 which short glandular divei-ticula are given ofi" in all dii'ections. 

 In its terminal pait, as is shown in figs. 1 8-20, the gland appears 

 to be differentiated into two portions : one lying nearei' the 

 oesophageal end of the stomach is lined by an epithelium loaded 

 with fine dark granules ; the other portion, lying nearer to the 

 mantle-cavity, is lined by an epithelium of the character shown 

 in PI. XXXIX. fig. 56. It is made up of large glandular cells, 

 oblong in outline, and filled with a highly refracting granular 

 substance which, when the cells are ready to discharge their 

 contents, is accumulated into oval pellets, as shown in the figure. 

 Between the gland-cells are long and very attenuated interstitial 

 cells, of which the outer ends ai'e expanded and produced to 

 form a cover ovei' the outei' ends of the gland-cells. The nuclei 

 of the interstitial cells lie in their expanded outer ends. I could 

 find no trace of cilia. In nearly every specimen examined the 

 mantle-cavity was full of a sticky gelatinous mass secieted by the 

 hypobi'anchial gland. 



From what precedes it is evident that the Helicinida^ are a very 

 homogeneous gi'oup, so far as their anatomical characters ai-e 

 concerned, and that such differences as I have been able to detect 

 are of very little assistance in classification, the resemblances and 

 differences in one set of organs suggesting one class of aflSnities, 

 those of another set of organs suggesting another class. Thus, 

 taking the arrangement of the coils of the intestine as a criterion, 

 we should place Alcadia, Orohophana, and Fakeohelicma close 

 together, with Lucidella related but somewhat apart : Eutrochatella 

 would go with Aphanoconia to form a distinct group. But if we 

 took the characters of the female gonaducts as a criterion we 

 should get a diffeient arrangement. Eutrochatella would stand 

 nearest to Alcadia, with Aphanoconia more distantly related : 

 Fakeohelicina with Orohophana would form a distinct group. 



The nervous system is so similar in all the species that it affords 

 a very slight guide, but, as far as the cerebral ganglia give any 

 clue, the genera would fall into an arrangement consistent with 

 their geographical distribution ; Alcadia, Lucidella, and Eutro- 

 chatella forming one group ; Palffohelicina, Orohophana, and 

 Aphanoconia another. Finally, the radular characters, which 

 have attracted a considerable share of the attention of systematists 

 and in my experience afford the most reliable and readily 



