LIFE-HISTOKIES OF OAMASINiE. 307 



which was taken by the earlier writers as the characteristic of the 

 so-called species G. marginatus ; this line was so narrow at first, 

 that it could scarcely be seen ; but as the eggs ripened in the ovary, 

 the abdomen became distended and the line became gradually 

 broader, particularly near the posterior margin, where the large 

 ripe egg (for one only is usually ripe at a time) generally lies. 



I bred from these males and females, and traced them through 

 a second generation with similar results. 



A point which struck me as singular, aud contrary to what has 

 been believed, was the absence of any inert stage before the changes 

 of skin, or from one stage to another. In the Oribatidse and other 

 Acarina which I have previously watched, each change is pre- 

 ceded by a period of such absolute quiescence that any person not 

 acquainted with the creature would suppose it to be dead ; not a 

 sign of life is to be obtained by touching it or otherwise. Megnin, 

 following Claparede's observations, is of opinion that during this 

 period the whole internal parts dissolve and reform ; and he ex- 

 pressly says that this is the case with the Gamasinse*. I am not 

 able to agree with him in this ; for certainly in no specimen which 

 I have bred have I been able to observe any inert period ; the crea- 

 ture has only become rather less active for a few hours ; and 

 among the thousands of Gamasids which I have had from time to 

 time I never noticed an inert specimen, although one is constantly 

 finding inert Oribatidse. 



Another somewhat important matter in which I do not find 

 myself able to arrive at the same conclusion as Megnin is the 

 period of copulation. Megnin was, I believe, the first to point 

 out that in the Dermaleichi (Analges) the adult male copulates, 

 not with the finally adult female, which possesses the strongly 

 marked external vulva, but with the female in an earlier stage, 

 which he calls nubile female (femelle accouplee), at which period 

 it closely resembles the nymph, and does not possess any external 

 vulva. Megnin points out that copulation takes place by the 

 anus ; and there cannot, I think, be any doubt that, with regard 

 to the Dermaleichi, he is right in both respects, subject to the 

 possible dispute as to whether his nubile female is actually dis- 

 tinct from the nymph ; he gives very good reasons for thinking 

 that it is. Megnin, however, does not stop here; he distinctly 

 asserts in his subsequent writings that these two points hold good, 



* Loc. tit. p. 323. 

 LINN. JOTJRN. — ZOOLOGY, VOL. XV. 24 



