. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. Fig. 54. â Division of ovum into the first two binstomercs. The polar body niarl;s the animal pole. (.Alter ) appears at the animal pole, the latter being indicated by the polar body. The depression deepens and extends as a meridional furrow round the egg. Finally, the division of the egg into two hah'es or blastomcres, which remain at- tached to one another, is completed, and the first stage in the segmentation of the Qg^ is accomplis
. Amphioxus and the ancestry of the vertebrates [microform]. Vertebrates; Chordata; Fishes; Ascidiacea; Vertébrés; Cordés; Poissons; Ascidiacés. Fig. 54. â Division of ovum into the first two binstomercs. The polar body niarl;s the animal pole. (.Alter ) appears at the animal pole, the latter being indicated by the polar body. The depression deepens and extends as a meridional furrow round the egg. Finally, the division of the egg into two hah'es or blastomcres, which remain at- tached to one another, is completed, and the first stage in the segmentation of the Qg^ is accomplished (Fig. 54). As it is beyond scoi)e of this book to discuss the mechan- ics of cell-division, the descrip- tion of the segmentation stages will be very brief. The first meridional cleavage which divides the egg into two blastomcrcs is followed by an- other one It riu-ht Tn"â¢'" l) (micn)meres) lie uptm four larger hlastcjmeres (tna- mcrCS agaUl nitO two. In this cromeres). Radial type of cleavage. way the stage with four equal (After !â¢:. m. \) blastomeres in one plane is produced. Next follows an equatorial cleavage, by which eight blastomeres are pro- duced, the four upper cells at the animal pole being some-. p;i :.?:"â g. 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 Willey, Arthur, 1867-1942. New York; London : Mcmillan
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectfishes, bookyear1894
