. Biology; the story of living things. sperm. ...mesooCarm. mesoderm onus V. segments 9 and 10, it receives sperm cells from the other worm that have been stored there. The girdle is passed down over the anterior end of the worm, slipped off, forming a closed case which contains the eggs, sperms, and a nutritive fluid. These capsules may be found in late spring under stones, boards, logs, or in manure heaps. After fertilization, the egg of the earthworm divides first into two, then four, then eight cells, and so on, continuing until a hollow ball of cells, called a hlastula, is formed. These c
. Biology; the story of living things. sperm. ...mesooCarm. mesoderm onus V. segments 9 and 10, it receives sperm cells from the other worm that have been stored there. The girdle is passed down over the anterior end of the worm, slipped off, forming a closed case which contains the eggs, sperms, and a nutritive fluid. These capsules may be found in late spring under stones, boards, logs, or in manure heaps. After fertilization, the egg of the earthworm divides first into two, then four, then eight cells, and so on, continuing until a hollow ball of cells, called a hlastula, is formed. These cells are not all the same size, larger cells appearing on the lower pole of the sphere, which begins to flatten and show a depres- sion, forming eventually a hollow cuplike affair, called the gastrula. This process known as gastrula- tion places the larger cells of the lower pole on the in- side of the cup where they become the endoderm, leaving the outer cells of the sphere to form the ectoderm. Meantime a third layer of cells which lies between the other two layers buds off and be- comes the mesoderm. This latter layer gives rise to the musculature, blood vessels, and most of the excretory and reproductive tissues ; the endoderm forms the food tube and much of the glandular material con- nected with it; the ectoderm gives rise to the epiderms, the nervous system and sense organs, and the outer portions of the nephridia, repro- ductive ducts, and digestive tracts. The young worms remain in th(^ egg case until they are about an inch in length. When first hatched they have no clitellum, since this organ appears only in mature 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 Hunter, George W. (George William), 1873-1948; Walter, Herbert Eugene, b. 1867; Hunter, George W. (George William), 1902-. New Yor
Size: 1540px × 1622px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorwalterherberteugeneb1867, bookcentury1900, bookpublish
