300 MR. A. D. MICHAEL ON THE VAEIATIONS IN THE 



coition, and which is discharged from thence into the vagina of the female. Had I been 

 foi'ced to rely upon this resemblance alone I should not have felt confident of the 

 function of the organ, because this minute cellular matter and glutinous fluid are not so 

 distinctive but what other products of the body might be mistaken for them ; but luckily 

 a closely allied species, Hcemogamasus Mrsutus, enabled me to decide the question ; it 

 has the domed elevation larger than in H. Iwmdus, and usually full of unmistakable 

 filamentous spei*matozoa, which often crowd the chamber as full as it will hold. 

 These spermatozoa measure about 30 ^u in length by abovit 1 i.i in breadth. 



It certainly seems strange that in two species so nearly related as Hcemogamasus hor- 

 ridus and S. Mrsutus the spermatozoa should in the first case be minute ovoid bodies, 

 and in the other long and filamentous ; it is impossible not to suspect that the latter is 

 the ultimate form into which the former at some time and under some circumstances 

 develops ; and this seems all the more probable because in S. Mrsutus the spermatozoa 

 retain the ovoid form until nearly the last, and it is only when they are about to enter 

 this chamber that they assume the filamentous form. The filament may be formed within 

 the ovoid, bu.t it cannot be distinguished. Although one cannot help being impressed 

 by this obvious idea, yet the facts are that the two species live together in the moles' nests 

 under precisely similar circumstances ; that I have examined them at practically all 

 seasons of the year, and have made extremely numerous dissections and sections in all 

 directions of both species, and yet in all cases where the chamber has not been empty 

 it has contained the minute ovoid bodies in //. horrklus and the filamentous in H. hir- 

 sutus. It cannot be suggested that they are the same species in difi'erent stages ; the 

 extremely dissimilar mandibles of the adult males (PI. XXXII. figs. 3, 9) and the epistomes 

 (figs. 5, 10, 11), to say nothing of the internal anatomy, would 2)ut this out of the 

 question ; and the females in both have mature eggs. 



I propose calling this domed chamber the camera spermatis. It will be seen later on 

 that spermatheca or rec-eptaculum seminis, in the ordinary sense, would scarcely be 

 applicable. 



Between the arms of the lyrate organ, but somewhat above and totally detached from 

 them, is another large and wholly undescribed organ, which is found only in the female ; 

 there is not a trace of it in the male. It is diflicult to give the measure of this because 

 it is dilatable and more or less elastic, and sulyect to endosmosis and exosmosis ; and it 

 is difficult to be sure what is exactly its normal size, if it liave any; but in every dissection 

 or section of a mature female H. horridns which I have made it has been a large organ, 

 often one of the largest in the body. It is a closed sac or vesicle with hyaline, trans- 

 parent, but not excessively thin, walls. The form is that of a cone witli curved sides and 

 rounded apex, or a bell witli a closed mouth (PI. XXXIV. figs. 48, 49, set). It extends 

 almost to the dorsal surface (PL XXXV. fig. 68, sa), is more or less horizontal, has the 

 base of tlie cone (or mouth of the bell) directed toward the rostrum, and the apex toward 

 the posterior end of the Acarid. It is generally slightly coated outside, either wholly or 

 partially, with loose granular matter, but this is not in any way a portion of the organ ; it is 

 easily cleaned oflF, and is to be regarded as embedding matter. I propose calling this organ 

 the sacculus foemineus. Its apex is not permanently closed, it is simply constricted, and 



