144 



different representatives of the Odonata with each other. Back- 

 HOFF (1910) has studied the development of the copulatory 

 apparatus in males of the genus Agrión {Cœnagrion Kirby) by 

 means of surface preparations and microtome sections, finding 

 no trace of these structures previous to the ante-penultimate 

 larval stage (instar) ; they arise from unpaired cell-masses and 

 show no indication at any time of origin from fusion of paired 

 rudiments, and hence cannot be homologised with the other 

 paired segmental appendages. His summar}^ of the differences 

 in the apparatus of the Zygoptera and of the Anisoptera re- 

 spectively ma}^ be expressed as follows : 



Zygoptera (regarded as the more primitive) : Penis un- 

 jointed ; its lumen communicating at its basal end with the body 

 cavity, but not with the seminal vesicle (vesicle of the penis), 

 and without a distal aperture to the exterior ; muscles, nerves, 

 and tracheae lacking from the copulatory apparatus. 



Anisoptera : Penis jointed ; its lumen not communicating 

 with the body cavity, but continuous with that of the seminal 

 vesicle, and having an opening to the exterior near its apex ; 

 muscles, nerves, and tracheie present in the copulatory apparatus. 



Nothing is yet known as to the details of the transference 

 of the spermatozoa from the ejaculatory duct until they reach 

 the female, and we are still entirely in the dark as to how the 

 localisation of the copulatory apparatus of the male, near the 

 anterior end of the abdomen, remote from his genital orifice, 

 came into existence, although Backhoff has suggested the re- 

 semblance in position of this apparatus to that of the genital 

 opening of the progoneate Arthropods. He infers, from the 

 palaeontological data of Handlirsch (1906-8), that this localisa- 

 tion occurred previous to Jurassic time. 



The Ovipositor: Its Development and its Reduction. 



We may turn naturally to the ovipositor of the female. The 

 late H. W, van der Weele gave us an extended account of the 

 Morphologie und Entwicklung der Gonapophysen der Odonaten in 

 1906. He confirmed the general results of Peytoureau (1895) 

 and Heymons (1896) that the gonapophyses are not the remains 

 or vestiges of embryonic abdominal limbs, but epidermal out- 



