46 THE NAUTILUS. 



of Polygyra tridentata the differentiation lias not gone so far, so that 

 while Dr. Pilsbry describes a mountain race with a more or less 

 double basal tooth, he hesitates to give it a name. Throughout the 

 paper the author, while naming a number of local races, shows a 

 natural reluctance to recognize in the nomenclature all the incipient 

 species which his studies have brought to light. As with the mam- 

 mals in the hands of Merriam, Allen, Rhoads and others, abundant 

 specimens with exact data have proved what the older authors did 

 not expect ; that everywhere segregation is going on, and that the 

 recognizable species and subspecies are far more numerous than we 

 had been led to suppose. Lord Salisbury's statement of a few r years 

 ago, that nobody had seen evolution actually going on in nature, ap- 

 pears absurd to the modern zoologist or botanist. Even the attitude 

 of those who do not believe in varietal nomenclature or the recogni- 

 tion of subspecies has changed. Thus Dr. Skinner, who from 

 sundry published opinions might be regarded as a " lumper," is 

 familiar with and has represented in his Splendid collection of butter- 

 flies more geographical races than entomologists dream of; and I 

 believe he will admit that if i;e were converted to the policy of 

 splitting, he might produce a work which would astonish us all. 



The writer of this notice believes that detailed studies like those 

 of Dr. Pilsbry are of the highest importance, from a philosophical 

 point of view, and that until zoologists are prepared to recognize the 

 wonderful complexity and variety of living forms, they cannot hope 

 to understand the larger problems of biology. And it seems to him, 

 furthermore, that we should be rational enough to weigh and con- 

 sider all characters, not merely those which strike the eye. We 

 think of the Sandwich Island Achatinellidre as being wonderfully 

 diverse., because their diversity is largely that of bright colors and 

 pretty patterns. Why may not the less conspicuous diversity of our 

 simply-colored snails be just as real, and just as worthy of recog- 

 nition by students of molluscan life? 



T. D. A. COCKERELL. 



THE ARMATURE OF HELICOID LAND SHELLS, by G. K. Gude 

 (Science Gossip). Mr. Gude has now brought to completion his 

 long series of articles on the genera Plectopylis and Gorilla, giving a 

 synopsis and key to the former group, a discussion of its geographic 



