THE THEORY OF SEX 



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given by a study of the copulatory organs. The nmth abdom- 

 inal segment of the female shows a pair of chitinous plates, 

 called laminae, which flank the genital opening. They can be 

 protruded by the aid of muscles which are inserted on chitinous 

 rods, the apophyses. In front of this organ we find the bursa 

 copulatrix, shown in figure 2 in ventral view. The male organs, 

 as represented in both ventral and side views in the micropho- 

 tographs figures 36 and 37 consist of a chitinous ring (the 9th 

 segment) carrying orally and ventrally a blind sac,- the saccus, 

 dorsally and aborally a curved hook, the uncus, right and left a 

 pair of forceps-like organs, the valvae; and in the median plane 



Fifiurc 2 



a long tube, the penis. The embryology of the organ shows that 

 the first anlage, already present in the caterpillar, is the Herold's 

 organ, from which penis and valvae later differentiate. At the 

 time of pupation the paired anlagen of the penis are fused, and 

 the anlagen of the valvae differentiate from the original 'Zapfen' 

 of Herold's organ. The uncus develops in the late pupal 

 stages and finally becomes curved. If we now study lowgrade 

 intersexual females, the first clear indication of male parts ap- 

 pears in this last developing organ, the uncus, whereas the last 

 male organs to appear in intersexuality are the first developing 

 penis and valvae. These important facts are illustrated in the 

 photographs 38 to 48, which represent the copulatory organs 

 of a series of intersexual females, corresponding closely to the 



