14 THE POPULAR SCIENCE MONTHLY. 



Prof. N. S. Shaler ! on the connection between the development of the 

 life and the physical conditions of the several continents, showing first 

 that the greatest amount of shore-line in proportion to the internal 

 areas indicates a greater diversity of surface within. 



Another proposition he attempts to establish : that in propor- 

 tion to the shortness of the shore-lines, or, in other words, to the 

 want of variety in their surfaces, will be the diversity of animal life 

 in the continent. He then proceeds from Darwin's standpoint, and 

 follows out many curious and instructive lines of thought regard- 

 ing increased amount of influences in diversified surfaces a level 

 plain having the same conditions throughout, but a mountainous re- 

 gion having for each one thousand feet of elevation a new condition 

 of things, in the form of streams, winds, humidity, and the like. In 

 areas of simple outline and unvarying surfaces w T e do, in fact, have a less 

 diversity of forms. 



Recognizing the mutation of continents through past geologic ages, 

 we again see the accompanying physical changes in not only modify- 

 ing forms, but in selecting them afterward by succeeding changes. 



The widely-diversified nature of the facts bearing on the doc- 

 trine of natural selection baffles all attempts at a systematic classifica- 

 tion of them. Of such a nature are many of the valuable communi- 

 cations of Prof. Wilder. 



At the meeting of this Association 2 he has, among other matters, 

 confirmed in a young lion the discovery of Prof. Flowers that, in the 

 young dog and probably in other carnivora as well, the scapho-lunar 

 bone has at the outset three centres of ossification, and that these 

 really represent the radiate intermedium and centrale of the typical 

 carpus. By study of a foetal manatee, Prof. Wilder is able to de- 

 termine its affinities, and to point out the probable retrograde meta- 

 morphosis of some ancient ungulate animal, and that the mana- 

 tee is widely removed from the whales Avith which it has been 

 associated. 



Mr. William K. Brooks has published a very remarkable paper on 

 certain free swimming tunicates, the /Salpa, giving for the first time 

 a clear and comprehensive history of certain ohscure points, and has 

 at the same time applied the principles of natural selection theoreti- 

 cally in showing the origin of salpa from sessile tunicates, and mak- 

 ing clear the peculiar modification of parts which accompany these 

 changes. 



In the field of entomology some capital work has been done, both 

 practical and theoretical. 



Prof. Riley's demonstration of the yucca-moth is unique in its 

 way. Dr. Engelmann has discovered that the yucca depends upon 

 insects for fertilization ; and Prof. Riley, by patient study, not only 



1 " Proceedings of the American Academy," vol. viii., p. 349. 



2 " Proceedings of the American Acc.demy of Arts and Sciences," vol. xxii., p. 301. 



