302 MR. A. D. MICHAEL ON THE VARIATIONS IN THE 



connective cuticle which binds the coxa of the third leg to the more chitinous part of its 

 acetabulum. 



Thus it will be seen that this series of organs or parts — the cornu sacculi, the sacculns 

 fcemineus, the rami sacculi, and the tubuli annulati, all of which are strictly confined to 

 the female — form an unbroken connection, varying enormously in size and capacity, but 

 absolutely continuous, between the sperm-chamber in the ovary and the acetabulum of 

 the third leg on each side. 



The position of these organs as regards the other viscera may be well gathered from 

 fig. 46, which was carefully drawn immediately after death from a female of Lcelaps 

 la?vis, after the dorsal plate, &c, had been removed. 



It will, I think, be convenient to describe some at least of the somewhat numerous 

 and wide variations of these organs which I have found in different species before treating 

 of their contents and supposed function. 



In describing all these parts, and, indeed, the internal anatomy generally, I cannot 

 too strongly insist upon the fact that two specimens are never really alike, and that the 

 same specimen varies with age and condition ; it is therefore only what may be called a 

 type-form in each case that can be described; but this type is never so widely departed 

 from but what it may be easily recognized in any dissection of the species, and may 

 probably therefore be considered as constant as could be anticipated. 



Hcemogamasus nidi (PI. XXXII. figs. 6, 7) is a smallish new species allied toiT. horridus, 

 and in which the female genital system is so similar that it is not necessary to give a 

 separate description of it. 



Lcelaps stabularis is a species in which the new organs above described correspond 

 more closely to those of H. horridus than in any other I have found, except H. nidi (see 

 PI. XXXI V". fig. 51). The differences, as will be seen by the figure, are that the lyrate organ 

 of L. stabularis is much more enlarged at its distal ends than that of H. horridus, and 

 forms broad, somewhat recurved plates ; that the cornu is wider in the lumen and much 

 less plainly marked off from the sacculus ; and that the rami are much longer, and the 

 ringed tubes consequently very much shorter, than in //. horridus. 



Hcemogamasus hirsutus is a species closely allied to II. horridus, belonging to the same 

 genus, and found with it under similar conditions ; and yet the organs we are discussing 

 differ far more widely from the same parts in H. horridus than those in L. stabularis do, 

 although the latter is a very different creature, belonging to a separate genus. The 

 lyrate organ of H. hirsutus (fig. 52) does not vary in any remarkable manner from that 

 of its ally, but when we examine the sacculus (fig. 53, sa) the contrast is very striking. 

 Instead of the large, simple, bell-shaped sac we have a small, more or less rhomboid, 

 organ placed transversely across the body ; the whole central part of the anterior side of 

 this is occupied by a shortish but very wide csecal prolongation running straight forw r ard 

 between the rami. Prom the posterior corners of the sacculus proceed two paired, almost 

 globular, diverticula, immensely larger than the sacculus itself, and joined to it by almost 

 imperceptible necks, with sharp lines of demarcation where they issue from the central 

 portion of the organ. These diverticula extend almost to the dorsal surface and are 

 quite clear and hyaline ; the position of one of them is shown in PI. XXXV. fig. 70, sd. 



