INTERNAL ANATOMY" OF THE GAMASID^E. 305 



chitinized walls, the two not quite touching. The strangest part of the construction, 

 however, is that hetween these two little globes, and attached to both, and I think (but 

 of this I am not certain) communicating with them, is a third little hollow, slightly 

 chitinized, vesicle, which is not quite a sphere, and from the outer end of which proceeds 

 a fine serpentine tube, with a bulbous end, which tube is wholly within the sacculus and 

 does not emerge at all. The sacculus, with the spheres and spheroid looking together 

 like a trefoil, and the third tube are seen in situ in fig. G3, and the trefoil, &c, dissected 

 out at fig. 64 ; both are carefully drawn from actual dissections ; a sagittal section through 

 the sacculus, showing one globe and the central spheroid and tube, will be found 

 at fig. 71, sa (PI. XXXV.). 



The last species in which I shall describe these organs is a new one found in 

 Tyrol. I propose calling it Laelaps Ugoniformis (fig. 65). In this curious creature the 

 lyrate organ is fully developed, but there is not any sacculus, cornu, or rami, only the 

 ringed tubes ; these run direct to the camera spermatis, and the two tubes join just at the 

 point where they enter the camera. In this species there exists something not found 

 in any of the others, viz., at or about the point w r here each ringed tube has its mouth in 

 the acetabulum of the leg there is a small elliptical receptacle (fig. 66), about 40 p in 

 long diameter, communicating with the exterior by a short stalk about 17 ^ long. I 

 had not enough specimens to investigate this species properly. 



All the sacculus organs in all species are apt, when empty, to shrivel up and be almost 

 impossible to find ; but they may then often be found by placing the creature, after the 

 dorsal plate has been dissected off, in water, when they fill by endosmosis and expand. 



It is to be remembered that the sacculus organs and ringed tubes are apparently 

 correlated with the lyrate organ. I have not found the one without the other in any 

 species; L. Ugoniformis is the nearest approach, but even there the ringed tubes are 

 present, while none of the species of the G. crassipes type, which I am acquainted with, 

 show any trace of either organ. 



We now come to the question of the contents and function of the sacculus foemineus 

 and its associated parts or diverticula. Of course the first obvious suggestion of 

 function, from the ending of the ringed tubes in the acetabula of the third legs, would be 

 that the whole structures were coxal glands; but, apart from the contents of the 

 sacculus, the equally obvious reply is that these organs exist only in the female, and 

 that if they were coxal glands they would exist in both sexes, as is the case with the 

 supercoxal glands of the Oribatidae, and the coxal glands of such other Acarina as are 

 known to possess those organs, including, according to Winkler, the Gamasinae, where 

 they are very small and totally unlike the organs I have been describing. Winkler 

 figures them in the male. 



The presence of the organs in the female only seems to confine our suggestions as to 

 their function to the generative system ; and all the other evidence which I have 

 obtained confirms this view. Omitting for the moment the very specialized species 

 Molotaspis marginatus and H. montivagus and their one or two allies, all the other 

 species investigated which possess the sacculus and its appendages usually have 

 contents therein. Taking again Hcemogamasus horridus and H. hirsutus as convenient 



SECOND SERIES. — ZOOLOGY, VOL. V. 45 



