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Show 190 ME. A. D. MICHAEL ON AN [Mar. 5, nuclei of about -01 mm. diameter, usually placed very regularly, which are best seeu in sections. The size and shape of the whole gland varies a good deal in different individuals, and probably at different times, but the average size may be considered to be about •1 m m . by about -07 m m . Although this is the larger of the two kidney-shaped salivary glands in Schaub's species it is not so in the present instance, the representatives of the other of the two being somewhat larger. This latter pair of glands (figs. 16, 23, sgq.) cannot be called kidney-shaped in the present species, each is more square with advancing rounded corners; they are not regular in shape, varying considerably in different individuals &c, still they preserve their general form ; they are flattened dorso-ventrally, and lie rather further back than the kidney-shaped pair; they are pressed against one another in the median line; and their posterior portions overlie and hide the anterior part of the brain, when seen from the dorsal side. The average size of each of these glands is about -11 m m . square. Simply for the sake of clearness I will speak of them in this paper as the "quadrate salivary glands." In spite of this general agreement in the form and position of these two pairs of glands with those described by Schaub and Croneberg, there is one leading point in which there is a very marked difference from them, and indeed from all similar glands vet described in tbe Acarina; and that is, that all the authors describe their glands, doubtless correctly, as discharging by a single duct; in the present species each of the four glands discharges most distinctly by two paired ducts (dq., dr.): whether this indicates the original derivation of each gland from tw7o which have coalesced, I am not prepared to say; they do not show any other signs which I can detect of a double origin; but the two ducts are clear and unmistakable. In the kidney-shaped glands the ducts spring from opposite sides of the gland a considerable distance apart; they are largest in diameter wiiere they leave the gland (about "01 mm.) and gradually diminish, their smallest part being where they enter the main general duct (there they are about •004 mm.) (fig. 16, dr.). The two ducts from each quadrate salivary gland (fig. 16, dq., fig. 21) spring from the underside of the gland near its anterior edge ; they arise some small distance apart, but considerably nearer together than those from the kidney-shaped gland ; they are also much finer and more transparent than those from the last-named gland, and enter the main general duct together, joining just before they enter. They often overlie one another; thus while it is perfectly easy to see the twT> ducts from the kidney-shaped glands, it requires very careful dissection to demonstrate those from the quadrate glands ; one of these must be dissected off, turned over to expose the under surface, and the two ducts separated with a very fine hair : if this trouble be taken then the two ducts are perfectly apparent, and their whole course may be traced to their entrance into the main general duct. I now come to the tubular salivary glands (fig. 16, sgt.); these, although essentially " tubular glands " are very different from, and much more |