. A text-book of invertebrate morphology. Invertebrates. 48 INVERTEBRATE MOBPHOLOGT. The transformation of the germ-cells present in an em bryo into spermatozoa is usually a somewhat complicated process. In the Round-worm Ascaris, in which it retains somewhat primitive characters, the process closely resem- bles what takes place during the maturation of the Fig. 22.âDiaguams to illustrate the Matukation op the Spkbm-cell. A = division of the spermogone. B = division of the two spermocytes. C = the four spermatids. B, E = conversion of a spermatid into a spermatozoon. W â fully developed
. A text-book of invertebrate morphology. Invertebrates. 48 INVERTEBRATE MOBPHOLOGT. The transformation of the germ-cells present in an em bryo into spermatozoa is usually a somewhat complicated process. In the Round-worm Ascaris, in which it retains somewhat primitive characters, the process closely resem- bles what takes place during the maturation of the Fig. 22.âDiaguams to illustrate the Matukation op the Spkbm-cell. A = division of the spermogone. B = division of the two spermocytes. C = the four spermatids. B, E = conversion of a spermatid into a spermatozoon. W â fully developed spermatozoon. The embryonic germ-cells {spermatogones. Fig. 22, J) undergo karyokinetic division, the number of chromosomes being, as in the ovum in the division which results in the formation of the first polar globule, twice that which is characteristic for the species. They do not undergo longitudinal division, and one half of them passes into one of the daughter cells (sper- matocytes) and the other half into the other, so that these two cells possess the number of chromosomes characteristic for the species. â A division of these daughter cells (Fig. 22, B) immediately takes place without a return to the resting stage, and unaccompanied by a longitudinal division of the chromo- somes, so that four cells (spermatids, Fig. 22, C) are formed each of which contains only half the typical number of chro- mosomes, and each one of these cells becomes a spermato- zoon. This ijrocess is comparable step by step with the. 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 McMurrich, J. Playfair (James Playfair), 1859-1939. New York, H. Holt and Company
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