150 Psyche [October 



In insects the anus is the direct development of the proctodseum, 

 and how a tergite can take part in the formation of a tube on the 

 ventral surface, without the position of the anus shifting during 

 ontogeny, I cannot understand. The onus of evidence lies with 

 those who claim such a development. 



Dr. Hopkins in a recent work ^ remarks: 



"It is quite evident that element a [median lobe'] represents 

 the tenth sternite, h [armature on internal sac] the tenth tergite, 

 c [tegnien] the ninth tergite, and d [spicule] the ninth sternite, 

 while hi and h2 [apical armature on internal sac] appear to repre- 

 sent elements of either the tenth tergites or of both the tenth 

 tergite and tenth sternite. It might also be well to consider in 

 future investigations the possibility of their representing the 

 tenth pleurites or even an additional eleventh segment." 



To me none of these statements are at all evident, and some are 

 quite illogical; all available evidence is against them. The most 

 important part of the organ, the internal sac, is not accounted for, 

 perhaps because it is membranous. Chitinization is often looked 

 upon as the important thing whilst the membrane is disregarded, 

 w^hereas the latter is the important part. This is certainly so in 

 the oedeagus of the vast majority of Coleoptera, the internal sac 

 being the chief organ and the armature (end plates) but secondary. 



As before remarked the stenazygos is formed by the invagina- 

 tion of the spot to which the threads from the testes are attached. 

 The zygos is supposed to be of mesodermic origin, but it appears 

 to develop continuously from the stenazygos. 



In the female pupa of R. ohscura the genital invagination takes 

 place down the middle of the ninth sternite. The "ovipositor" 

 is composed of modified body segments or of sternites, the genital 

 styles being developed directly from the appendages of the ninth 

 segment of the larva and pupa. The ovary is at first composed of 

 two small cells which lengthen out and meet together at one end; 

 these are in touch with one another and the end of the oviduct for 

 some time before the walls break down and communication between 

 the two ovaries and the duct is established. The oviduct appears 

 to be a continuous development of the azygos or uterus and there- 



1 Preliminary Classification of the Superfamily Scolytoidea. U. S. Dept. Agr., Tech. Ser. 17, 

 Pt. II, 1915. 



2 Explanatory remarks in brackets are by the present writer. 



