CROSSING TWO HEMIPTEROUS SPECIES. 223 



development of the intromittent organ which, when present, is 

 functionally a necessary adjunct of the glands, and as indicative 

 of the sex as the reproductive glands themselves. If we cannot 

 accept the mode of transmission of the intromittent organ as an 

 index of the mode of transmission of the reproductive glands, 

 it would seem necessary to discard all structural features or other 

 characters, which are distinctive of the gonads of a given species, 

 such as their distinctions in size, form, color, etc., and assume 

 that these characters, associated with the gland, have a different 

 mode of transmission from the gland itself. 



This would prevent any experimental test being applied to 

 the chromosome theories of sex-determination and leave free 

 scope for the wildest cytological speculations. If we should 

 place the intromittent organ in the group of secondary sexual 

 characters, because it has certain features in common with these 

 characters we ought logically to place the reproductive glands 

 themselves in the same group. For example, both these organs, 

 in common with most of the secondary sexual characters, can 

 be transmitted to the opposite sex hermaphrodites appearing 

 in forms that are normally sexually distinct. A case in point is 

 Goodrichs's '12 interesting and important discovery of a male 

 amphioxus in which 49 of the gonads were testes containing 

 ripe spermatozoa and one was an ovary containing ripe ova. 

 It may be urged that the intromittent organ is a secondary 

 sexual character on the evidence that in the development of the 

 embryo it appears much later than do the gonads this indicating 

 that the gonads are more fundamental and stable morphological 

 entities. But there are facts opposed to this interpretation- 

 Smith '10 found that when the spider crab is infected by the 

 parasite sacculina, the testes can become so greatly metamor- 

 phosed that some of the cells may develop into ova and the same 

 testis contain both ripe ova and spermatozoa. 



It would seem that the division between primary and secondary 

 sexual characters in common with almost all attempts at classi- 

 fication, has the objection that the line of demarcation is not, 

 at all points, perfectly clear; but we believe, in spite of this, that 

 we are justified in classing the intromittent organ as a primary 

 sexual character and that the results from the study of the trans- 



