. . of the nutritive oo cells. The four cells grow together in one compact massto a great size, the partitioning membranes being,however, traceable. They bulge out the membrane ofthe genital tube into the body cavity. In successfulpreparations, fine nuclei of a tesselated follicularepithelium can be found between the eggs and thismembrane (Fig. 33, w). When the egg has been dis-charged down the branch into the genital tube, thelocus of the egg is found as a small shrunken bag fullof minute round bodies which are doubtless thesefollic
. . of the nutritive oo cells. The four cells grow together in one compact massto a great size, the partitioning membranes being,however, traceable. They bulge out the membrane ofthe genital tube into the body cavity. In successfulpreparations, fine nuclei of a tesselated follicularepithelium can be found between the eggs and thismembrane (Fig. 33, w). When the egg has been dis-charged down the branch into the genital tube, thelocus of the egg is found as a small shrunken bag fullof minute round bodies which are doubtless thesefollicle cells thrown off by the shrinking of the mem-brane (Fig. 33,6). This epithelium then apparentlyplays no very important part, unless, in some way, it 144 THE PART I brings about the contraction of the membrane for thedischarge of the eggs. The nuclei of the nutritive cells grow to an enor-mous size, and clearly play the chief part in absorbingmaterial for the formation of the yolk. When theegg is ripe, these nuclei come to the surface andgradually FIG. 33.—Eggs at different stages. In stage i the definitive egg nucleus is alreadydifferentiated from the nuclei of the three nutritive cells; the latter are seen togrow very large and coarse, and then in 5 to move to the side where theyeventually disappear. In 5 the yolk discs fill the whole egg, making the nucleusdifficult to see. At 6 an egg has been discharged ; the follicular membrane hasshrunk, its contents being probably dislodged epithelial cells, f, testes asoccasionally found ( in A. cancriformis)\ n, nuclei of follicular epithelium. The egg, in its passage down the genital tube andalong the longitudinal oviduct, gets covered with aslimy substance yielded by the deep club-shapedepithelial cells. This substance hardens into a shellfor the protection of the egg, a shell which, as VonSiebold remarks, looks as if made of hardened eggs pass out between the loth and nth pairs of SECT, x REPRODUCTION 1
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherlondo, bookyear1892
