Papers Volume 8 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...of the lumen of the hydrocoele and of its lobes were also modeled. For making the reconstructions Bom's method was employed, with plates of beeswax brought to the proper consistency by mixing with Venice turpentine. All of the drawings were made from camera-lucida outlines taken with Zeiss objective and oculars 4 and 6. Figures 4 to 15 were again 129 enlarged with camera drawings magnifying to twice the number of diameters. Figures 2 to 15 have been taken from the 55-hour specimens, all others from the 29. INTERNAL STRUCTURE. The body of the 29-hour plutei of Laganum is ovoid in shape, in some cases almost spherical, with a flattened or slightly concave anterior surface (fig. 1). Two larval arms grow out from a position somewhat dorsal to the center of the antero-lateral regions. In the 55-hour specimens, the body has elongated slightly and the posterior end has become somewhat pointed. In the earlier stage the arms extend outward at an angle of about 60 from the body, while in the older form they are more slender and reach upward nearly parallel to each other. An opening to the exterior lies in the center or slightly to the right of the center of the flattened anterior surface. It may be seen readily in the whole mount, but no other opening can be observed. The animal itself is exceedingly opaque, so that no study of the internal organs could be made except in specimens especially fixed and bleached for observance of the skeletal structures. Unfortunately, in this detailed treatment the tissues were so largely destroyed that study of them was impossible. Among the specimens studied, about fifty in all, I have found three which show interesting variation in structure--two with 3 larval arms, and one with 5. In the former case the third larval arm arises fro...