298 Mr. H. M. Bernard on 



dismissed the question of hermaphroditism with the words 

 " certainly the appearances which have come under my notice 

 favour this view." The efforts kindly made at the time by 

 Prof. Howes to obtain specially preserved specimens of Apus 

 were unsuccessful. 



On returning once more to the slides which show the her- 

 maphrodite condition of the genital glands, I have been 

 somewhat surprised to find how much en evidence the sperm- 

 centres are. In each case the first section, passing well 

 through the genital gland, shows almost immediately what is 

 wanted. It is quite impossible that they could have been 

 overlooked had they occurred in any of the specimens in 

 which they are reported to be absent. They show, however, 

 certain variations which make it highly probable that in each 

 species the phenomenon is a normal one under certain life- 

 conditions, the nature of which we can only surmise. 



In what follows, in order to avoid circumlocution, I shall 

 always speak of the cells which I believe to be sperm-cells 

 under this name, while admitting that some different interpre- 

 tation may perhaps have to be put upon them. 



The S-pitzbergen Variety of Lepidurus glacialis. 



In all the specimens examined the epithelium of the poste- 

 rior portion of the genital tube is modified to a varying extent 

 in the manner illustrated. Fig. 1 (PI. XI.) is a longitudinal 

 section through this portion of the genital gland in a specimen 

 measuring about 1 centim. long. The genital tube is seen 

 resting on the ventral longitudinal muscle-strand, separated 

 from it, however, by the membrane (m) which encircles the 

 intestinal tube and the genital glands *. The segmental 

 bulgings of the tube gradually diminish posteriorly, but are 

 indicated even to the tip. This tip appears in the section as 

 if separated from the rest, but this is simply because the sec- 

 tion here passes somewhat tangentially. The drawing repre- 

 sents the appearance of the section when only a low power is 

 used. The most anterior swelling shown in the figure occurs 

 in about the thirteenth trunk-segment, *". e. two behind the 

 one which opens externally at the base of the eleventh leg. 

 The two descending muscles run into the twenty-third and 

 twenty-fourth appendages. 



Figure 2 shows a portion of the same section as seen under 

 a "6 millim. apochromatic oil imm. (1"40 n. a.) of Zeiss. The 



* ' The Apodidae,' pp. li'O and i ; 97 ; also fig. 14, p. 59. 



