i8 9 6. NOTES AND COMMENTS. 153 



is the only one that can be depended upon with certainty. " A few 

 drops of a 5 per cent, solution of cocain were mixed with the water 

 in which the Aplysias were. After a time they expanded fully. 

 They were then left in the solution (twelve hours or more) till no con- 

 traction took place when removed and put into weak alcohol. If con- 

 traction took place, they would be put back into the cocain solution 

 when they again expanded. This was repeated till no contraction 

 took place, when they could, after a time, be put into stronger 

 alcohol." 



The Hinge of Bivalve Shells. 



The development and morphology of the hinge in bivalve 

 Mollusca is a subject that needs much further elucidation, since it 

 is sure to lead to a better understanding of the inter-relationships of 

 the various members of the class Pelecypoda, and so possibly to a 

 more satisfactory system of classification. A first step in this 

 direction has been taken by Dr. Felix Bernard, of whose valuable 

 work a first instalment appears in the Bulletin de la Societe Geologique 

 de France (3 e ser., torn, xxiii., pp. 104-154). We hope to be 

 able to lay before our readers a full account of Dr. Bernard's 

 researches at some later period when the rest of his paper shall see the 

 light. Meantime, one or two of his results are worthy of special 

 attention. He passes over the embryonic or prodissoconch stage, 

 and taking up his researches from that point, finds, so far as he has 

 gone, that there are two typical forms of embryonic shell. In the 

 second place, he finds that the ligament always arises internally in a 

 triangular pit that slants obliquely backwards. Hitherto it has 

 generally been believed that the external ligament was the phylo- 

 genetic predecessor. The growth of the ligament affects the curva- 

 ture of the umbones. He proposes a new notation for the teeth, using 

 odd numbers for those in the right valve and even numbers for those in 

 the left. Dr. Bernard then describes the development of the hinge 

 as shown in a series of stages from the young to the adult individual, 

 and illustrates them with simple but excellent figures. Any con- 

 clusions at which he may have arrived concerning the possible con- 

 nections between the different forms of hinge are reserved for his 

 further communication, when other genera shall have been studied. 



Concerning Snails. 



Under Mr. Pilsbry's fostering care, the Pulmonata are being 

 brought into better order than they have been for many a long day. 

 He has just (Nautilus, February, 1896) established two new "super- 

 families," or, as we should say, sub-orders. The one, Aulacopoda, is to 

 include the Zonitidae, Limacidae, Endodontidse, Arionidae, and Philo- 

 mycidae, the characteristic of the group being the presence of grooves 

 that run one on each side the whole length of the foot, a short 



