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THE AMEBIC AN NATURALIST [VOL. XLTV 



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. The remainder of the 

 literature on the secondary sexual phenomena of 

 araneads contains for the most part only casual observa- 

 tions, without attempts at analysis. 



I. Some General Mating Relations 

 For a correct understanding of the points at issue it 

 would be very desirable to have ample data on the 

 numerical proportions of the sexes, but unfortunately 

 little is known on this head. What is known is brought 

 together in another paper of mine (1908a) ; and there 

 also it was found in the case of Lathrodectus mactans 

 that the "average male ratio (number of the males 

 divided by the number of the females) is 8.19, deter- 

 mined from a count of 41,749 newly hatched spiderlings." 

 In this species the adults differ most markedly, and the 

 young emerging from a cocoon are readily separable into 

 two groups, distinguishable not only by size relations, but 

 also, as specially indicated by me, by differences in the 

 form proportions of the abdomina. Those spiderlings 

 with a flatter dorsum and more anterior pedicel were 

 considered to be males, for this is one of the characters 

 in which the adults differ. However, none of these 

 spiderlings were raised to maturity, though the attempt 

 was made to do so; no differences in the internal genital 

 organs can be found at the time of hatching, and occa- 

 sionally (though rarely) nearly intermediate forms occur 

 between the two groups of spiderlings. There is then 

 room for doubt whether the two groups represent males 

 and females, respectively, and the sex-ratio is not securely 

 established from my results; it is rather in the nature 

 of a strong probability. Beyond this case nothing 

 definite is known about the numerical proportions of the 

 sexes. 



