235 



THE MALE GENITALIA OF THE COCKROACH, PERI- 

 PLANETA ORIENTALIS, LINN., AND THEIR HOMOLOQY 

 WITH THE GENITALIA IN DIPTERA. 



By W. Wesche. F.R.M.S. 



{Read January \lth, 1908.) 

 Plates 19 and 20. 



The sexual armature of the male of Periplaneta has every part 

 present (or its homologue) that is found in the most elaborate 

 combination in the Musciclae, but it is extraordinarily difficult to 

 understand and homologise, as every piece is asymmetrical. In 

 many species of the Orthoptera, fertilisation is brought about by 

 the male transferring a spermatophore to the cloaca of the 

 female ; Dr. Benjamin Lowne thinks that this is most probably 

 the method by which the cockroach is impregnated.* Certainly 

 there are no signs of an ejaculatory duct in the penis, though 

 the other parts are highly organised, and it can be seen that the 

 elaborate apparatus found in other insects for storing and con- 

 trolling the flow of spermatozoa, is represented by an equally, or 

 even more elaborate apparatus for storing and protecting the 

 spermatophore. Bearing in mind the great probability of Dr. 

 Lowne's suggestion, not only as coming from so high an authority 

 on insect anatomy, but supported by the details of the structure, 

 we may conjecture that the genitalia of this order of insects are not 

 (unlike the mouth parts) of archaic type, but are a specialisation, 

 which has resulted in the complete transformation of the 

 mechanism of the whole organ, and of the functions of its parts, 

 the ejaculatory duct changing its course and opening in the 

 centre under the part whict I call the cover (PI. 20, Fig. 6), while 

 a special gland is present, opening between the paraphalli, which 

 has functions probably connected with the formation of the 

 spermatophore. I shall show later that the palpi usually present 

 * The Anatomy, Physiology, etc., of the Blow-fly, p. 664 (1895). 



