10 Canadian Record of Science. 



of mussel, Unio Complanatus and Unio Yentricosus, botli 

 found living together iu the St. Lawrence at Verdun. 



IT) O 



Unio Complanatus has a long, narrow, comparatively flat 

 shell. Unio Ventricosus, a shorter, broader and deeply 

 arched shell. iSTow the first has a structure similar in all 

 respects to that of Anodonta, which is the typical species 

 described in zoological text books. The inner lobe of the 

 inner gill is attached to the foot only in front and the 

 outer gill is used as a nursery for the young. In Unio 

 Yentricosus, on the other hand, the inner lobe of the 

 inner gill is attached to the foot for the whole of its 

 length and only the hinder part of the outer gill is used 

 for a nursery. Here are two well marked anatomical 

 facts correlated with a difference in the shells of two 

 species of the same genus, and there are numerous other 

 minor differences which I have not mentioned. It is 

 exceedingly important to pursue this line of investigation 

 further. 



To sum up, the day is past when a natural history 

 society could be held to justify its existence by the mere 

 collecting and naming of species. Its function certainly is 

 to collect, but that only as a means to an end, namely, 

 to determine the conditions of the problems which it has 

 to attack. From this point of view, whilst there is 

 everything to be said in favor of making collections of 

 total species, there is equally much to be said against 

 spending time in making collections of species from all 

 parts of the world, and especially against mixing species 

 from different localities. Once the local fauna is fairly 

 well known, the object of the naturalist is to study each 

 species in relation to its environment, and leaving to the 

 anatomist the task of elucidating the past history and 

 wider relationships of an animal from its internal struc- 

 ture to determine what effect its present surroundings 

 have had on it ; in a word, to study evolution in action. 



