12 Transactions of the Society. 



space inclosed within the ring ; thus the whole organ looks like an 

 old-fashioned watch-pocket. This will be understood most easily from 

 figs. 14, 15. It must be remembered that those figures are drawn as 

 though the spectator were looking straight upward from below. In 

 consequence of this formation only the anterior half of the ring is 

 really open for the passage of the egg, but it is, of course, possible 

 that at the moment of the egg passing the transverse bar may bend a 

 little and the membrane stretch a little ; but even then the opening 

 would be very much smaller than the egg that has to pass through it. 

 The inside of the parietes of the pocket is provided with several 

 transverse rows of long, closely-set teeth or villous processes, not 

 probably hard enough to be properly called teeth or spines, but yet 

 stronger and firmer than ordinary hairs. The roof of the vestibule 

 above the open (anterior) half of the ring is covered by a thin 

 chitinous plate, of which the transverse bar before mentioned forms 

 the posterior edge. The median portion of this plate is plain, without 

 processes, the plain part forms about one-third of the width. The 

 outer portion, all along the lateral and anterior regions of the plate, is 

 occupied by a series of radiating lines of processes similar in nature 

 to those above described, but larger. Sometimes these processes 

 spring from slight ridges, and the part of the plate which carries 

 them is slightly convex, although the form of the plate taken as 

 a whole is concave. The large, but more or less soft, egg must be 

 forced through the comparatively small opening of the vestibule and 

 between all these processes. I am not able to say with certainty 

 what the office of these processes is, as I have not ever succeeded in 

 seeing one of the creatures in the act of oviposition. Winkler 

 suggests that the office of certain scattered chitinous spines, which he 

 found in what he calls the " vagina," is to hold, and prevent the 

 escape of, the spermatophores or balls of spermatozoa which he found 

 in that organ. I am fully aware that some species of the genus 

 Gamasus are fecundated by the introduction of spermatophores into 

 the genital opening of the female ; indeed, in the year 1886 I pointed 

 out that this was the case in at least one species of the genus, and I 

 also described the process by which it was effected, which I had been 

 fortunate enough to observe.* I can scarcely think, however, that 

 the retention of spermatophores is the sole office of so elaborate an 

 organ as the vestibule of Uropoda Krameri ; an organ very different 

 apparently from the female genital opening in Winkler's species; 

 particularly as I have not noticed spermatophores or balls of sper- 

 matozoa in the vestibule of Uropoda Krameri. Three possible further 

 uses suggest themselves, viz. firstly, that the processes are simply to 

 exclude dust, &c. ; this, however, is not altogether probable, as the 

 vestibule is covered exteriorly by the closely fitting genital plate; 

 and, moreover, neither this idea nor that of retention of spermato- 

 phores, would explain the presence of similar processes on the inside 



* "Observations iipon a Species of Gamasus supposed to be unrecorded,'' 

 Journ. Quek. Micr. Club, ii. (1886) pp. 263-4. 



