126 DARWINISM TO-DAY. 



to the Darwinian conclusions ; and, second, on a basis of the care- 

 ful scrutiny of the facts of secondary sexual differences, the author 

 finding sexual selection wholly unable to account for the great 

 majority of secondary sexual characters among animals. 



2 Plate, L., "Uber die Bedeutung des Darwin'schen Selections- 

 prinzips," pp. 107-111, 2d. ed., 1903, Leipzig. 



8 Darwin outlined the theory of sexual selection in the "Origin 

 of Species" (1859), but first treated it at length in the "Descent of 

 Man" (Parts II and III), 1871. 



4 Wallace, A. R., "Tropical Nature," chap, v, 1878; and "Darwin- 

 ism," chap, x, 1891, London. 



6 Doane (Ent. News, Vol. XVIII, pp. 136-138, 1907) has described 

 the striking behaviour during mating of certain Dolichopodid flies 

 (Scellus virago, n. sp.) observed by him on the salt marsh flats 

 of San Francisco Bay, near Stanford University. In these matings 

 it is the female which is the active sex in pursuing and exciting 

 the other. 



6 See note 2. 



I Morgan, T. H., "Evolution and Adaptation," chap, vi, 1903, 

 New York. This chapter is an exhaustive attack on the theory of 

 sexual selection. 



8 Mayer, A. G., "On the Mating Instinct in Moths," Psyche, Vol. 

 IX, pp. 15-20, 1900. 



9 Mayer, A. G., and Soule, C. G., "Some Reactions of Cater- 

 pillars and Moths," Jour. Exper. ZooL, Vol. Ill, pp. 427-431, 1906. 



10 Douglass, N. G., "On the Darwinian Hypothesis of Sexual 

 Selection," Nat. Science, Vol. VII, pp., 398-406, 1895. 



II Diirigen, "Deutschlands Amphibien u. Reptilien," p. 89, 1897. 



12 Cunningham, J. T., "Sexual Dimorphism in the Animal King- 

 dom," 1900. 



13 Wolff, Gustav, "Beitrage zur Kritik der Darwin'schen Lehre/* 

 p. 21 ff., 1898, Leipzig. A bitter but keen and trenchant critical ex- 

 position of certain weaknesses in the selection theories. He criti- 

 cises the theory of sexual selection in the following words : 



"An diese Falle reiht sich vielleicht am besten die Betrachtung 

 der Folgen, welche fruhzeitige Sterilitat auf die Ausbildung von 

 Wolff's exposi- sekundaren Geschlechtscharakteren ausubt. Wir kon- 

 tionofweak- nen ja diese Erscheinungen auch in gewissem Sinne 

 nesses in sexual zu den Ruckbildungen rechnen ; sie haben aber insbe- 

 selection, sondere auch das mit den vorigen Fallen gemeinsam, 



dass wir hier ebenfalls einen im individuellen Leben des Organismus 

 sich abspielenden Vorgang beobachten konnen, der nach der Selek- 

 tionstheorie nicht eintreten durfte. 



"Nach der Selektionstheorie entstehen ja sekundare Geschlechts- 



