252 The Irish Naturalist. December. 



A NEO-LAMARCKIAN. 



" Use-Inheritance, illustrated by the Direction of Hair on the Bodies 

 of Animals." By Walter Kidd, m.d., f.z.s. London: A. & C. 

 Black, 1901 ; 8vo ; pp. 47. Price 2s. 6d. net. 



In this little volume, hardly more than a bound pamphlet, Dr. Kidd 

 has given a popular account of his researches on the distribution of the 

 body hair of Mammals, and the conclusions they have led him to ; and we 

 must congratulate him on the admirable way in which he has introduced 

 the general public to facts hitherto veiled in the learned pages of the Jour- 

 nal of Anatomy and Physiology and the Proceedings of the Zoological Society. 

 It has been known that the slope of the hair is displayed in the foetus 

 before birth, since Bschricht described and figured it in 1837. Our author 

 has investigated this point in a large number of animals, and found great 

 constancy in each group, with only such differences as indicate problems 

 to be solved. For purposes of description it is necessary to have a 

 proper nomenclature, and the terms chosen are readily comprehensible. 

 A whorl is a group of hairs radiating from a given point, and usually 

 forming a diverging spiral. & feather is a short tract which has its hairs 

 diverging obliquel}-, feather-like, from a median line, and usually starts 

 from a whorl at one end. A crest is a line bounding two diverging sheets 

 of hairs; usually a feather, which starts at a whorl, terminates at a crest, 

 and, indeed, at its sides, is bounded by a pair of crests. This relation 

 may well be studied on the face of the horse, short hair, of course, giving 

 the most typical appearances. A whorl is obvious in our own heads, as 

 in those of the apes, towards the point of the lambdoid suture, whence 

 the hair radiates to front, sides, and back, and the special reason for this 

 appears to be that with long hair on a convex spheroidal surface, some 

 such arrangement is necessary. With the other whorls, this explanation 

 will not serve, and Dr. Kidd regards their appearance in all other regions 

 as the expression of dynamical causes, for: — '' 1. They all occur where 

 opposing traction of underlying muscles is found. 2. They never occur 

 over the middle of a large muscle, and seldom in a place where there 

 is not a hollow or groove in the superficial anatomy. 3. They are 

 most uniform and most marked in animals with very strong muscles, 

 and those that are actively locomotive. 4. Their constancy appears to 

 depend upon range of action and activity of function of the muscles 

 in the part and individual animal affected." The formation of whorls 

 under these conditions is compared with that of dimples in the human 

 face. 



As the muscles whose action is involved have not yet come into use 

 at the time when the slope of the hair follicles, inducing the slope of the 

 hairs, is decided in the embryo, we have to choose between the assump- 

 tion that this slope is sufficiently important to have "selection value," 

 and to have decided for each group the survival of those that possessed 

 it, or else to admit the author's thesis, that the arrangements are due to 

 "use-inheritance." Such a book as this is calculated, at least, to give 

 pause to the Weismanniaus. Dr. Kidd has broken ground in a command- 

 ing position, and we are anxious to see how his attack can be met. 



Marcus Hartog. 



