OCR Text |
Show 1885.] GLANDS OF MYGALE. 5 third lobes are shorter, thicker, and directed transversely; they extend slightly beyond the edges of the entosternite, and descend a little way into the coxae of the fourth and fifth appendages. In addition to these four coxal prolongations, the gland has again two internal projections near its middle third. These projections correspond to two slight excavations of the entosternite, between its lower plate and its upper prolongations. The latter pass above the gland between its coxal lobes, so that only the extremities of these can be seen between the prolongations of the entosternite. The annular stomach, which rests on the entosternite, sends its lateral diverticula between these superior prolongations. The four posterior diverticula of the stomach l pass above the lobes of the coxal gland, are then bent back, and pass between the muscles of the corresponding coxae, and extend below the cepalothoracic ganglion. The colour of the gland is uniform, a brownish yellow not unlike that of the stomach and its lateral diverticula. Its appearance is coarsely cellular, showing distinctly the groups of cells of which it is made up. I have nowhere seen any efferent duct, either passing to the exterior, or to any internal organ. The gland in Mygale, like that of the adult Limulus and Scorpio, is therefore a closed gland. The shape and position of the coxal gland, as I have observed them in this large South-American Mygale, do not represent an isolated fact or one peculiar to this species alone. The diagram Plate II. fig. 2 shows in fact that in Mygale cosmentaria, and consequently in all the Tetrapneumones, the relations of the gland are almost completely identical2. When it is possible to study fresh specimens of Limulus, Scorpio, and Mygale, 1 think it would be useful to examine the contents of the gland from the chemical point of view. The result of such an examination would certainly help to determine the physiological function of this curious organ3. EXPLANATION OF PLATE II. Fig. 1. Diagram of a transverse section of the cephalothorax of Mygale ccetnen-taria, Latr. ( X 9), passing through the coxa; of the third pair of ambulatory legs, and showing the relations of the right coxal gland (a) with the entosternite {E) and the digestive apparatus ; d, lateral 1 In addition to the four large pairs of lateral diverticula, there is also a small anterior pair, at the base of the first lateral pair. (See Plate II. fig. 4.) 2 The slight difference which is to be observed in the diagram fig. 2, on the inner side of the gland at the base of the fifth pair of appendages, was probably caused by the fact that this point corresponds to a certain number of imperfect sections. I think that for the rest, the diagram is sufficiently exact; and if one were to examine the coxal gland of Mygale cosmentaria, I think it would be found that its shape is very near to that indicated by the diagram. 3 P.S.-March 20th, 1885. After the reading of this paper, I was able to consult Blanchard's " Organisation du regne animal." In the fig. 2, pi. xvi. (Arachnides) of this work, one can recognize the coxal gland in the so-called " glande stomacale." But the corresponding text, unfortunately, does not exist.-P. P. |