. Outlines of zoology. Zoology. ,) Fig. 31.—Embryos—(1) of bird; (2) of man.—After His. The latter about twenty-seven days old. , Yolk-sac ; pi., placenta. of some Coelentera—two-layered, externally ciliated, oval forms without a mouth. (3) The fact of recapitulation.—It is a matter of experi- ence that we recapitulate in some measure the history of our ancestors. Embryologists have made this fact most vivid, by showing that the individual animal develops along a path the stations of which correspond to some extent with the steps of ancestral history. (1) The simplest animals are singl
. Outlines of zoology. Zoology. ,) Fig. 31.—Embryos—(1) of bird; (2) of man.—After His. The latter about twenty-seven days old. , Yolk-sac ; pi., placenta. of some Coelentera—two-layered, externally ciliated, oval forms without a mouth. (3) The fact of recapitulation.—It is a matter of experi- ence that we recapitulate in some measure the history of our ancestors. Embryologists have made this fact most vivid, by showing that the individual animal develops along a path the stations of which correspond to some extent with the steps of ancestral history. (1) The simplest animals are single cells (Protozoa). (2) The next simplest are balls of cells ( Volvox). (3) The next simplest are two- layered sacs of cells ( Hydra). (1) The first stage of development is a single cell (fertilised ovum). (2) The next is a ball of cells (blastula or morula). (3) The next is a two-layered sac of cells (gastrula).. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
Size: 1388px × 1800px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
