142 



SCIENCE 



[N. S. Vol. LI. No. 1310 



Incidentally, the object of these experi- 

 ments is by no means restricted to the taking 

 of photographs in the earth's atmosphere, al- 

 though this application may have more uses 

 than were at first suspected. 



Eegarding the ultimate developments of 

 the method, I do not wish to leave the im- 

 pression that these will be restricted to re- 

 searches in or near the earth's atmosphere. 

 On the contrary, every one of the matters so 

 far proposed is, as I have already main- 

 tained, based upon sound physical principles, 

 and can therefore be realized. Further, there 

 are additional principles, the application of 

 which is certain to lead to results of even 

 greater interest and importance. All these 

 results will be realized, however, not by argu- 

 ment and discussion, but by the application 

 of real research methods to the problems that 

 are waiting to be solved. 



Egbert H. Goddakd 

 Claek College, 



WoKCESTEE, Massachusetts 



SCIENTIFIC BOOKS 



Studies on the Variation, Distribution, and 

 Evolution of the Genus Partula. The 

 Species Inhabiting Tahiti. By Henky Ed- 

 ward Crampton. 313 pp., 34 plates, 252 

 tables, Y text figures. Publication N"o. 228 

 of the Carnegie Institution of Washington, 

 January, 1917. 



Interest having been diverted from pure 

 science by the war, no adequate review has 

 appeared of this monumental and funda- 

 mentally important work which represents the 

 results of four journeys of exploration made 

 by its author in Polynesia; in the course of 

 which more than 75,000 adult snails were 

 collected together with over 7,000 adolescent 

 individuals; more than 200 of the valleys of 

 the Society Islands having been visited for 

 this purpose. 



The present volume deals with snails from 

 Tahiti alone, and the thorough, scholarly, 

 and conservative treatment given the subject 

 renders this work of paramount value to all 

 future students of the variations of Partula. 

 Not alone were variations and distribution 



of the adult snails studied, but the yoimg 

 contained in the brood pouches of the adults 

 were dissected out, thus throwing light upon 

 the fecundity of each variety, and the ratio 

 of elimination of the young before they can 

 reach maturity. 



Crampton shows that these snails are not 

 found in the dry low-lands along the shore, 

 nor do they occur in the cold regions of the 

 high peaks of the interior, for a temperature 

 of 55°-60° P., stops their activity. The 

 snails are therefore restricted to the relatively 

 moist deeply wooded troughs of the inter- 

 mediate regions of the valleys where they are 

 commonly found during the day-time on the 

 undersides of the leaves of the banana, wild 

 plantain, caladium, turmeric, wild ginger and 

 dracffina. 



The ridges between valleys are generally 

 dry, and thus the snail population of each 

 valley is more or less isolated. Crampton finds 

 that these snails descend from the trees and 

 bushes and feed during the night, or on moist 

 days, upon decaying vegetation. The young 

 and adolescent being more active in this feed- 

 ing reaction than are the adults. 



It has long been known from Garrett's 

 studies that the Tahitian species of Partula 

 like the Achatinella of Oahu varied from 

 valley to valley, some forms ranging over a 

 wide area while others are restricted to a 

 single valley, or even to a limited region 

 within a valley. 



In general moreover the farther apart two 

 valleys the wider the diversity between their 

 snails, although this is not always the case. 

 Crampton's work has the merit of giving 

 precision to our hitherto more or less vague 

 knowledge of the distribution of the 8 species 

 of Partula found in Tahiti. He shows con- 

 clusively that great changes have occurred 

 since Garrett studied the snails, in 1861-1884, 

 and that in some cases the species have spread 

 over wider areas, and in the interval have 

 produced some new sub-species or varieties. 

 Thus the fascinating picture of a race in 

 active process of evolution is presented. The 

 details of this process are rendered clear by 

 the excellent photographs of relief maps, and 



