60 THE GENETIC AND THE OPERATIVE EVIDENCE 



gratuitous assumptions as to the cause of the evolution of the male 

 and female, enough still remains in Montgomery's own observations 

 to include his results on courtship under Darwin's theory of sexual 

 selection. For example, Montgomery says: 



"The adult male is excited simultaneously by fear of and desire for the 

 female, and his courtship motions are for the most part exaggerations of ordi- 

 nary motions of fear and timidity. By such motions he advertises himself to 

 the female as a male, but there is no proof that he consciously seeks to arouse 

 her eagerness by esthetic display — there seems to be no good reason to hold 



that the female is actuated in her choice by sensations of beauty 



Thus my opinion was opposed to Darwin's theory." 



Now, it is obvious that if a more brightly colored male has a better 

 chance of " advertising himself" to the female all the essential require- 

 ments of Darwin's theory are fulfilled, regardless of whether the male 

 is conscious of his ornamentation or the female makes use of an " esthe- 

 tic sense." In another passage (p. 173) Montgomery concedes all 

 that any modern critical advocate of Darwin's theory is likely to ask: 



"We have previously seen that conscious aesthetic choice by the female 

 probably does not account for such male characters [secondary sexual charac- 

 ters with their 'conspicuous color markings']; that they are accordingly, 

 probably not due to sexual selection. These characters of the males may be 

 most readily explained as being conceived by simple natural selection. Pecu- 

 liar ornamentation would be selected because unusually greater sex recogni- 

 tion therefore prompted mating." 



It is evident that Montgomery has only shifted the situation, although 

 to advantage, I think, but is essentially in accord with Darwin's theory 

 of sexual selection, despite his protest to the contrary. The difference 

 lies in Darwin's and especially in the Peckhams' use of the term 

 " choice," "aesthetic sense," etc., to stand for the fact that the female 

 more promptly mates (as Montgomery prefers to put it) with a male 

 peculiarly ornamental. 



The most critical observations on sexual selection that have been 

 made in the group of insects are those by Sturtevant on the pomace 

 fly. The courtship is described as follows : 



"The first and most noticeable act in courtship occurs when the male, being 

 near the female, extends one wing at about right angles to his body, and 

 vibrates it for a few seconds. The wing is then returned to the normal position 

 and the process is repeated, usually with the other wing. But between times 

 there is a scissors-like movement of the wings repeated several times. This 

 vibrating of the wings is often repeated many times, and may be done in any 

 position relative to the female, though the male always faces her. Usually, 

 in fact, he swings quickly around her in a semicircle once, or oftener, during 

 the process. Soon the male begins to protrude his genitalia and, if the female 

 remains quiet, to lick her posterior end. Some white matter now protrudes 

 from her ovipositor, and other males in the same vial are usually observed to 

 become excited now and begin courting, indicating odor as a cause of sexual 

 excitement. If the female runs or flies away the male is excited, moves his 



