A. D. MICHAEL ON THE ACARINA. 227 



opinion that the penis of the male was inserted, not in the anus of 

 the female, but into the curious conical projection characteristic of 

 the adult females of the genus Glyciphagus, which projection is 

 higher in level than the anus. As far as I am aware, no other ob- 

 server has ever treated this projection as anything except as what 

 Murray calls it " an anal button," although it was known to be 

 tubular, but I cannot help thinking that it is the female copulative 

 organ, and I find that it has a projection or serration of the lower 

 edge which appears fitted to admit and clasp the male one. The 

 ventral aspect of this female projection is like Fig. 6, and its 

 dorsal aspect like Fig. 5, which I have drawn from an allied species, 

 G. spinipes, in which the projection is better shown. 



The next curious point in the reproductive organs of the Acarina, 

 to which I will shortly refer, is the position of the male organ in 

 the Cheyletidce, treating them as a family according to Megnin's 

 view, and including Myobia, Barpirliynchus, &c, in that family. 

 In all other A carina with which I am acquainted, the penis is either 

 placed on, or emerges through, the ventral surface of the abdomen, 

 or the sternal surface of the cephalothorax. In the Acari proper, 

 the male organ is external on the sternal surface of the cephalo- 

 thorax. In the Gamasince., Trombidiino?, &c, it is retracted within 

 the body, but emerges in the same position as in the Acari proper. 

 In the Oribatidce, Halicarinw, &c, it is retracted, but emerges on 

 the ventral surface of the abdomen, the aperture being closed when 

 not in use by what may be called chitinous folding doors, but in 

 the Cheyletiche the penis emerges on the dorsal or notogastral sur- 

 face, by an aperture not closed by any door ; the position of this 

 aperture varies, in Cheyletus venustissimus, C. parasitivorax, &c, 

 it is close in front of the terminal anus, in C. macronycus, My- 

 obia musculi, &c, it is almost in the middle of, or rather further 

 forward, in, the notogaster {i.e., the dorsal surface of the abdo- 

 men), and in Harpirynchus nidulans it is on the dorsal surface of 

 the cephalothorax. This dorsal position of the penis, which was 

 observed by Claparede in Myobia musculi, struck him as something 

 quite unique in nature, but it appears to exist throughout the family, 

 and Professor -Semper, of Wurtzbourg, in his treatise upon the 

 11 Affinities of the Articulata and Annelida with the Vertebrata," 

 expresses his opinion that the position of organs relatively to the 

 ground has not the importance which Baer attributes to it, and says, 

 amongst other things, that in many Annelids the opening of the 



