. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 122 ANNALS OF THE SOUTH AFRICAN MUSEUM (a) The end sac The end sac differs from that of the well-known Astacus in not being exposed on the dorsal surface of the labyrinth. As in Anomura and Palinurus (Marchal, 1892), it is completely enveloped by the labyrinth and therefore can only be properly identified in sectioned material (figs 40, 41). It is relatively voluminous and has a fairly distinct central cavity (fig. 40) which is located more or less dorso-laterally in the middle of the main lobe of th
. Annals of the South African Museum = Annale van die Suid-Afrikaanse Museum. Natural history. 122 ANNALS OF THE SOUTH AFRICAN MUSEUM (a) The end sac The end sac differs from that of the well-known Astacus in not being exposed on the dorsal surface of the labyrinth. As in Anomura and Palinurus (Marchal, 1892), it is completely enveloped by the labyrinth and therefore can only be properly identified in sectioned material (figs 40, 41). It is relatively voluminous and has a fairly distinct central cavity (fig. 40) which is located more or less dorso-laterally in the middle of the main lobe of the labyrinth. From this numerous branches radiate in all directions into the interstices of the labyrinth, so that the body of the gland is a compound of both the end sac and the labyrinth. Waite's (1899) statement that in Homarus the end sac is a derivative of the embryonic coelom and that the remainder of the gland is ectodermal in origin has been quoted in several subsequent publications; but Manton (1928, 1934) has shown that both the duct and the end sac are mesodermal and that only the tube which leads to the exterior is ectodermal. Functional differences of the parts may account for the marked histological contrast betw^een the walls of the end sac and the labyrinth in J. lalandii. The wall of the end sac is formed by a delicate layer of rather irregular cells (fig. 41), each of which contains a large nucleus and faintly staining granular contents and is 11-5 to 14-3 /x high. i ncJusion. nucleus Fig. 41. Transverse section of wall of end sac. (b) The labyrinth The labyrinth is the spongy mass forming the bulk of the antennal gland and \vhich, for descriptive purposes, may be divided into a main lobe and a white lobe. The main lobe (figs 38, 39) constitutes the posterior part of the labyrinth lying adjacent to the anterior apodeme of the mandible. It is cream coloured, and when \iewed laterally is roughly quadrangular in outline with its antero- ventral extremity usually c
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectnaturalhistory, booky
