THE EXTERNAL GENERATIVE ORGANS. 731 



because sections are not well adapted to throw light upon the 

 subject. I have, therefore, thought it well to give an account 

 of what is known from the observations of other observers on 

 various Insects which exhibit more favourable conditions. 



Development of the External Organs of Generation. Ouljanin 

 [373], in 1872, traced the development of the sting in the hive 

 Bee to imaginal discs, and concluded that it consists of modi- 

 fied abdominal limbs. Krapelin [374] traced the development 

 of the external genital organs in the male Bee to a similar 

 source ; and Packard [372] states that, in Insects generally, 

 ' the male genital organ is originally composed of three pairs 

 of tubercles (two pairs apparently in ./Escbna) arising from the 

 ninth abdominal ring.' The latter is undoubtedly, as already 

 stated, a complex of several somites. 



The most detailed description of the development of these 

 organs in both sexes is found in a paper by Dewitz [375]. He 

 has arrived at the following conclusions : 



In the female, the sting, or ovipositor, consists of six 

 principal parts, of which two are frequently united into a 

 median organ : these are developed from six ventral papillae. 

 Two arise from the ante-penultimate somite, and four from 

 the penultimate somite of the larva or nymph. These papillae 

 are developed from imaginal discs, similar to those from which 

 the thoracic limbs of Corethra are developed. 



In the Hymenoptera these discs are primarily involutions of 

 the hypoderrnis, but in the Locusts they first appear as project- 

 ing papillae. 



Dewitz says that these papillee are not developed in the 

 same order in all Insects. In the male larvae of the species 

 observed only two papillae were developed on the penultimate 

 somite, and none apparently exist on the ante-penultimate 

 somite. This statement does not agree with the observations 

 of Packard, and the discrepancy probably arises from different 

 species having been investigated. 



Dewitz regards it doubtful whether the four papillae on the 

 penultimate somite are to be regarded as two pairs of limbs, or 

 as a single pair of biramous appendages. There appears to be 



