REVIEWS 369 



for causality. No doubt the origin of sexually differentiated qualities may be 

 physiological, and the mechanism of distribution may be in some such fashion 

 as Mendelian analysis suggests, but it would be comfortable to our intelligence 

 if we could associate the control and elaboration of secondary sexual characters 

 with some utilitarian principle. 



Mr. Mottram points out that individuals of a species are not of equal value ; 

 the female as she often is pregnant, or may become pregnant, can secure the 

 maintenance of the species, but any single male is never independently the 

 vehicle of species-maintenance ; young animals, as they have more life in front 

 of them, are more valuable than old animals. Next, he points out that individuals 

 form themselves into societies such as pairs, families, and herds. Next, that indi- 

 viduals vary in structure, male from female, young from old. He correlates these three 

 sets of facts, the presence of unequal value with difference of structure, and of 

 both with the formation of societies. His argument follows that natural selection 

 must appreciate differences in structure, that it must treat associations as units, 

 bring about diversity of structure in them, and bring it about that the less valuable 

 individuals are more liable to destruction than the more valuable individuals. 



Mr. Mottram's theory or working hypothesis must be put to the test by a study 

 of conspicuousness in nature, and he has paved the way for this by giving many 

 illustrative examples. Conspicuousness, he points out, may be of use as a 

 signal to friends, a form of utility which does not bear on his argument, or 

 a signal to enemies, and in this latter case, it may serve either to warn them 

 off or to attract them. Attracting conspicuousness may serve to draw off the 

 attack of the enemy from the more valuable to the less valuable individuals of 

 a species or members of a society, and if this, in fact, happen to any great degree, 

 then natural selection would encourage differences in structure and habit, dis- 

 tinguishing the less valuable from the more valuable. Innumerable examples can 

 be produced which are harmonious with Mr. Mottram's view. Conspicuously 

 coloured birds make themselves even more obvious to an enemy by movements 

 which concentrate attention on themselves and divert it from the concealed 

 and protectively coloured young squatting in the turf. Cock birds sing perched 

 in the open or high in the air, loudly advertising their presence, whilst the 

 hen covers the eggs or the young in a secretly placed nest. A cloud of bright 

 males, the destruction of any of which brings no harm to the species, mob the more 

 precious female, with the result that the chances of her destruction by an enemy 

 are very small. 



It would not be difficult to allege cases of difficulty, and no doubt this will 

 be done, but until the large inquiry for which Mr. Mottram asks has been carried 

 out, it would be impossible to guess on which side the balance lies, and we 

 can certainly congratulate the author on the clearness and value of his statements. 



Evolution "by Co-operation : A study in Bio-Economics. By H. Reinheimer. 

 [Pp. xiii -f 199.] (London : Kegan Paul, 1913.) 



Unfortunately it is easy to be unjust to Mr. Reinheimer's treatise, as it is 

 written in a diffuse fashion with a good deal of repetition and an unprepossessing 

 acceptance of popular and expert writers as equivalent authorities. The back- 

 ground of the argument, which from time to time surges up into the foreground of 

 the picture, is an ardent desire to interpret evolution as a moral process. It seems 

 intolerable to Mr. Reinheimer that what he regards as virtue should go unrewarded 

 or what he deems vice unpunished in the organic world. Advance in organisation 



