. The embryology and metamorphosis of the Macroura. Crustacea; Embryology -- Crustacea. FIG. 1.—Diagrams of transverse sections through the alimentary tract of an embryo of Alplicux aaulcyi u liich is nearly ready to hatch, to show tin- origin of I In- gastric uland It tun tlie postero lateral lobes of the in id gut. Si (tion I cats tbo hindgut and lobes of the "liver," Section ill the. hinduut. \\-hero it merges into the mcsenti ion. :i:i'. ;/;/% Secoudai y lobules of tii'J ' . UO, liindent ; nKj1, posti i o lateral lol" s ol inidgllt. The development of the meseuteron can be u
. The embryology and metamorphosis of the Macroura. Crustacea; Embryology -- Crustacea. FIG. 1.—Diagrams of transverse sections through the alimentary tract of an embryo of Alplicux aaulcyi u liich is nearly ready to hatch, to show tin- origin of I In- gastric uland It tun tlie postero lateral lobes of the in id gut. Si (tion I cats tbo hindgut and lobes of the "liver," Section ill the. hinduut. \\-hero it merges into the mcsenti ion. :i:i'. ;/;/% Secoudai y lobules of tii'J ' . UO, liindent ; nKj1, posti i o lateral lol" s ol inidgllt. The development of the meseuteron can be understood by reference to Figs. 162-165, 168, and 185. The endodermal epithelium spreads by the division of its own cells and by accession of cells from the yolk, both forward over the nervous system and upward against the sides of the body. This is shown in the series of horizontal sections (Fig. 162-165). Fig. 168 which is from an embryo a little more advanced, shows that the endoderm is rising from the nervous cord near its point of flexure, into ti transverse vertical fold. Simultaneously with the upward growth of this ventral fold, two dorsal longitudinal folds grow downward, and finally unite with the ventral fold and with each other, thus constricting oil' from the alimentary tract two lateral pouches, the pri irary lobes of the " ; The folds grow forward and the constriction proceeds gradually with the growth of the embryo. This process is illustrated by the diagrams (Fig. 1) which were drawn from tin embryo near the point of hatching. The histology of the endoderm as shown in Fig. 173, is essentially the same as in the previous stage. The cells are prismatic, and the. undent spherical, and, as in all stages, filled with numerous nucleoli or chromatiu balls. The cell walls are very delicate ?.ud the protoplasm often contains large US. I''n:. 2.— .Semidia:;raiiin>atic representation of tho alimentary tract and , :i|>poudii};e» in
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Keywords: ., bookauthor, bookcentury1800, bookdecade1890, booksubjectcrustacea
