The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . Figs. 180, 181.—Haliphysema primordiale, an extant I8O0 External view of the whole spindle-shaped animal (attached by-its foot to seaweed). Fig. 181. Longitudinal section of the same. Theprimitive intestine (d) opens at its upper end in the primitive mouth (m).Between the (g) lie amoeboid eggs (e). The skin-layer (h) belowis encrusted with grains of sand, above with sponge-spicules. opening at the top is the mouth-opening (Fig. 181, m).The two cell-strata forming
The evolution of man : a popular exposition of the principal points of human ontogeny and phylogeny . Figs. 180, 181.—Haliphysema primordiale, an extant I8O0 External view of the whole spindle-shaped animal (attached by-its foot to seaweed). Fig. 181. Longitudinal section of the same. Theprimitive intestine (d) opens at its upper end in the primitive mouth (m).Between the (g) lie amoeboid eggs (e). The skin-layer (h) belowis encrusted with grains of sand, above with sponge-spicules. opening at the top is the mouth-opening (Fig. 181, m).The two cell-strata forming the wall of the pouch are the 68 THE EVOLUTION OF MAN. two primary germ-layers. These most simple Plant-Animalsdiffer from the gastrula principally in the fact that theformer are attached by one end (that opposite to the mouth-opening) to the bottom of the sea, while the latter arefree. Moreover, the cells of the skin-layer are coalescent andhave included many foreign bodies, such as sponge-spicules,sand-grains, etc., which serve to support the body-wall(Fig. 180). The intestinal layer, on the
Size: 966px × 2588px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookdecade1870, booksubjectembryologyhuman
