INTEENAL ANATOMY OP BDELLA. 49.5, 



Scbaub's " smaller dorsal mouth-gland " iu Eydrodroma, if the place where the duct 

 discharges, and the cunuectiou of that duct Ije, as usual, taken as dcteriuiniug the homo- 

 logies ; but as it may be possible that this giaud is more to be regarded as the homolo'>'uo 

 of the small gland which discharges by the duct " c/i^' in Tliyas petrophilus (fig. 10 ia 

 my paper, 14), I have thought it best not to use the name " quadrate salivary eland" 

 lor the gland in question: for the sake of clearness I shall call it the "anterior 

 salivary giaud " in this paper. It is a rather small, rounded, or heart-shaped gland ]yin<» 

 in the anterior corner of the dorsal vertex, and its posterior side is closely pressed a"-aiust 

 the front end of the reniform gland when the two are in situ ; so that it is very difficult 

 to distinguish this gland from tbe reniform in sections, and, indeed, it can only be done 

 by the thin ttuiica propria which envelops the gland, and Ijy the fact that the anterior 

 salivary gland stains more deeply than the reniform, and has a slightly ditferent histolu- 

 giciil structure, its secretion is a mass of dark-coloured granules. 



The Fericibal Salloary Glands. — The two other paired salivary ^lands (fio's. 10 

 and oli sgp) lie one on each side of the receptaculum cibi (sucking-stomachj, and clasp that 

 organ ; they are apparently the " preventricuiai- glands " of Karpelles (8). These glands,, 

 which I will call the pericibal salivary glands *, bear considerable resemblance in "-eneral 

 form and appearance to the reniform gland, against which their outer sides are closely 

 pressed ; like it they stand on edge in the body, and are a flattened oval or almost 

 elliptic ; the outer sides adapt themselves to the form of the inner sides of the reni- 

 form giaud, while their inner sides adapt themselves to the receptaculum cibi (suckino-- 

 stomach); they embrace practically almost the whole sides of that organ except the 

 narrow neck, and by an increase in their thickness they curl over the top of its posterior 

 portion. They are composed of large cells nidiating from a centre and provided with 

 large and distinct roundish nuclei and nucleoli ; the cells, however, are not so lar"-e as 

 those of the reniform gland. The contents of these cells stain deeply with hematoxylin, 

 and then present more the appearance of a network, and less of granulation than those 

 of the reniform gland. In the centre of the gland, where the apices of the cells come 

 together, there is a very minute open sx)ace from which the duct starts. There is a 

 small valve at the commencement of ihe duct of this, and indeed of each of the paired 

 glands except the tubular, formed by the thickening of the walls of the duct, so as to 

 constitute tAvo labia pressed against each other. The duct itself is long and fine ; in 

 well-preserved specimens it exhibits a slightly ringed structure of its inner coat ; it 

 passes along the side of the receptaculum cibi (sucking-stomach) in an almost straight 

 Une, goes just below the chitinous bridge and chitinous roof, and discharges by a small 

 opening just at the proximal corner of the epipharynx (tig. 2, dpj). From the position 

 of the mouth of the duct it would appear probable that this gland is a true salivary 

 gland ; whether those that discharge by the common duct into the space between the 

 mandibles and above the chitinous bridge have the same function must be more 

 doubtful ; it would seem possible that they lubricate the mandibles, but glands of such 

 importance would scarcely be wanted for that purpose only. 



* I do not use Karpellcs's name of " preventriculur glands," because they are not iiomologous with the "-lands 

 which bear that name in the UribatidiB. 



67* 



