214 



SCIENCE 



[N. S. Vol. XXXIV. No. ! 



less the nematocysts have important defensive 

 value to the ilatworm. 



Wm. a. Kepner 

 Biological Laboratory, 

 University of Virginia, 

 July 15, 1911 



Arthur 

 Pp. 177, 



Professor 



SCIENTIFIC BOOKS 

 Convergence in Evolution. By 



WiLLEY. London, John Murray. 



32 figs. 1911. 



In " Convergence in Evolution 

 Willey has written an illuminating exposition 

 of the wide-spread occurrence of convergence 

 in animal structure and habit, and a strong 

 argument for a fairer recognition of its valid- 

 ity and importance. Indeed, this argument 

 is sometimes so strong, at least in its wording, 

 that it seems almost to overshoot the mark. 

 It makes convergence seem too important, too 

 dominant, too universal, to be true. For ex- 

 ample — perhaps a slightly unfair one, wrested 

 thus from its context — Professor Willey says 

 of histologic identity : 



In the light of facts which are now available it 

 even begins to appear strange, although only a 

 matter of a few years or months ago, that histolog- 

 ical identity should ever have been insisted upon 

 as a criterion of homology except within well-de- 

 fined limits (p. 153). 



But despite his enthusiasm for convergence 

 and his avowed intent to unseat homology 

 from its high place. Professor Willey never 

 means to be unfair. He is simply a con- 

 vinced believer, a positive expositor and a 

 strong debater. He asks only for a recogni- 

 tion of the facts. He has no laws of con- 

 vergence to offer any more than he will agree 

 to accept any one universal criterion of 

 homology. 



Then away with laws and away with criteria 

 until they cease to obscure the facts as they are 

 (p. 170). 



The book is thoroughly interesting reading 

 for a zoologist. It is a mine of illustrations 

 of adaptive convergence. Indeed, it might be 

 offered as a reference book of animal adapta- 

 tions. Examples of extraordinary similarities 

 in superficial and histologic structure in all 

 parts of the bodies of animals of all the phyla 



crowd the pages of the book. Eor not a few 

 of these the author is able to draw on his own 

 contributions to the knowledge of animal 

 morphology. For the others he usually gives 

 satisfactory references. 



I am tempted to take out of the book some 

 of the choice examples. But I shall be doing 

 my readers a greater favor if by refraining 

 from doing this, and at the same time telling 

 them how interesting and suggestive many of 

 of these examples are, I can induce them to 

 see the whole book. To read it as a whole is 

 the more desirable also because of the un- 

 usually independent and original points of 

 view from which the author examines many 

 current biological theories and problems. In- 

 deed the book is so refreshing and stimula- 

 ting in its forthright outspokenness with re- 

 gard to much that many of us feel insurgent 

 about but hesitate to speak out about, that it 

 is worth while for this alone. All the con- 

 vergence in it will be surplus for your money! 



Just one thing to act as " snapper " at the 

 end of this otherwise unmitigated enthusiasm 

 of commendation. The style in which the 

 book is written is unfortunate. Not as to 

 sentence construction, paragraphs, grammar, 

 punctuation, but as to abruptness of attack 

 and of leaving off; of pertinence of matter 

 to subject, of illustration to point. One 

 loses his bearings too often in the book. One 

 wonders whether this example belongs to the 

 subject behind it or to the one in front of it. 

 Or indeed whether it belongs in the book at 

 all. But readers of scientific books are, from 

 long experience, immune to most of the diffi- 

 culties which unusual manners of writing can 

 present. They are accustomed to dig their 

 gold wherever and however they find it con- 

 cealed. And Professor Willey's book has 

 much good gold in it for any digger. 



V. L. K. 



Stanford University, Cal. 



A Monograph of the Naiades of Pennsyl- 

 vania. By Arnold E. Ortmann, Ph.D. 

 Memoirs of the Carnegie Museum, TV., 

 No. 6, February, 1911, pp. 279-347; pi. 86- 

 89; 4to. 



