October 1, 1886.] 



SCIENCiJ. 



309 



gathers in puppoi-t of the hypothesis of physio- 

 logical selection, on the segregation of the fit. 

 Domesticated varieties cannot show much evi- 

 dence for physiological selection, because breeders 

 keep their strains separate artificially, and this kind 

 of variation is not in their inteiTst. They do 

 show very strongly, however, how important it 

 is to prevent intercrossing with the parent forms if 

 the varietal form is to maintain itself. It is hardly 

 possible that a species could he formed without 

 the prevention of intercrossing with other forms : 

 it is even difficult to imagine any single variation 

 so intensely useful as to i-esist the -swamping 

 effects of free intercrossing. In the natural state 

 the variation in question would not be noticed 

 until the process were over ; an.d so, as is the case 

 with natural selection, the process cannot be 

 directly observed. But it can be proved that the 

 kind of variation ^vhich the theory requires does 

 occur in nature and under domestication. If the 

 season of fiow^ering or pairmg were advanced or 

 retarded (and changes in the environment would 

 frequently produce the result), the conditions for 

 physiological selection would be given. 



But physiological selection will be best shown 

 in what may be termed ' spontaneous variability 

 of the reproductive system.' Of this fact we have 

 evidence in individuals {e.g., Mr. Darwin observes 

 that "it is by no means rare to find certain males 

 and females which will not breed together, though 

 both are known to be perfectly fertile with other 

 males and females"), in races (e.g., under domesti- 

 cation, " the yellow and white varieties (of Verbas- 

 cum), when crossed, produce less seed than the 

 similarly colored varieties " — Darwin), in species 

 (for, as the distinction between varieties and species 

 is of degree only, and as the main distinction is as 

 regards mutual sterility, every instance of sterility 

 between parent and varietal forms is evidence of 

 the action of jihysiological selection). 



Dr. Romanes then proceeds to show that ' ' the 

 facts of organic nature are such as they ought to 

 be, if it is true that physiological selection has 

 played any considerable part in their causation ; " 

 and to do this he shows that the three cardinal 

 objections to the theory of natural selection — 

 namely, sterility, intercrossing, and inutility — find 

 a ready explanation in the hypotliesis of jjliysiolo- 

 gical selection. In this evidence it is brought out 

 that in all probability the variation in the repro- 

 ductive system is the primitive and distinctive 

 one in the formation of species, and not that it 

 was develojied as secondary to another specific 

 distinction in any other part of the organism. 

 In addition, it is shown that the theory is capable 

 of explaining why species have multiplied, and 

 have not become transmuted in a linear series, 



and that the large body of favorable evidence 

 furnished by the geographical distribution of or- 

 ganic life is perhaps the strongest argument for 

 the truth of the theory. For the details of these 

 points, reference must be made to the original 

 paper. 



A word as to the relation of the theories of 

 natural and of physiological selection. It has 

 already been noticed that the kind of evidence 

 on which each depends is alike ; that the former 

 deals with the origin of genera, families, orders, 

 and classes, even more than that of species, while 

 the latter relates to species alone ; that the former 

 perpetuates useful distinctions alone, while the 

 latter takes up the non-adaptive kind. It remains 

 to add, that the two theories are in no way op- 

 posed to one another, but are complementary and 

 co-operative. Without physiological selection, 

 natural selection would be overcome by the ad- 

 verse influences of free intercrossing : without 

 natural selection, physiological selection could 

 perpetuate no difl'erences of specific type other 

 than those of mutual sterility and trivial details of 

 structure, form, or color. 



In conclusion. Dr. Romanes suggests the fol- 

 lowing experimental verification of his theory, 

 and asks the co-operation of observers in different 

 geographical areas. The experiment consists in 

 taking well-marked natural varieties of plants, and 

 testing the relative degrees of fertility, first within 

 themselves, and next towards one another ; in 

 continuing the process " in successive years over 

 a number of natural varieties, by carefully con- 

 ducted artificial fertilization, and by counting the 

 seeds and tabulating the resulfs." 



LAUNHARDTS MATHEMATICAL ECO- 

 NOMICS. 



Professor Launhardt has made what seems 

 to us quite a notable contribution to the literature 

 of mathematical economics in the volume before 

 us. Whatever may be thought of the importance 

 of investigations of this nature, it cannot be denied 

 that the works of the principal writers on the 

 mathematical theory of political economy — Cour- 

 not, Walras, Jevons, and perhaps others — are 

 marked by insight as well as ingenuity, and ip 

 many respects by true scientific method as well 

 as scientific form. They have nothing in com- 

 mon with that pseudo-science which we occasion- 

 ally find endeavoring to conceal its emptiness be- 

 hind a breastwork of mathematical formulas. 



Professor Launhardt bases the theory of political 

 economy on the Walras-Jevons idea of utility in 



Mathematische hegrilndung der volkswirthschaftslehre. 

 By WiLHELM Launhardt. Leipzig, Engelmann, 1885. 8°. 



