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 [874] traced the development 
of the external genital organs in the male Bee to a similar 
source; and Packard [872] states that, in Insects generally, 
‘the male genital organ is originally composed of three pairs 
of tubercles (two pairs apparently in A2schna) 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 [875]. 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 papille. 
Two arise from the ante-penultimate somite, and four from 
the penultimate somite of the larva or nymph. These papillz 
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 hypodermis, but in the Locusts they first appear as project- 
ing papille. 
Dewitz says that these papilla 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 papilla 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 
