Journal of experimental zoology . best set forth byConklin. It has, however, been impossible to follow these sub-stances far by cytological methods, so that their fate is largely amatter of conjecture. In the egg of Chaetopterus such substances,oxy-chromatin, are similarly set free, and, in addition to these,there is liberated at each mitosis a group of large granules that canbe followed through at least one cell-generation m each are the bodies that Mead described in the first cleavage asnucleoli. Their history in the first cleavage is briefly as follows: Theyarise in connection wi
Journal of experimental zoology . best set forth byConklin. It has, however, been impossible to follow these sub-stances far by cytological methods, so that their fate is largely amatter of conjecture. In the egg of Chaetopterus such substances,oxy-chromatin, are similarly set free, and, in addition to these,there is liberated at each mitosis a group of large granules that canbe followed through at least one cell-generation m each are the bodies that Mead described in the first cleavage asnucleoli. Their history in the first cleavage is briefly as follows: Theyarise in connection with the chromosomes from the segmentationnucleus and separate from them in the prophase of the first divi-sion. So that the equatorial plate consists of a certain number 202 Frank R. Lilhe of chromosomes with intermingled granules. The latter arehardly larger at this time than the ends of the chromosomes, andthey stain in iron-haematoxylin even more intensely than the chro-mosomes themselves. Only the chromosomes divide and in the. \/.£ Fig. 29. Outline of longitudinal axial section of the completed two-celled stage. Toshow the transmission of chromatin masses cut off from the chromosomes exclusively to thelarger cell. The fine dotted outline shows the boundary of the spherular endoplasm. E, Ectoplasm;, ectoplasmic defect; c, chromatin masses cut off from the chromosomes; N, nucleus; ,polar ectoplasm. anaphase the granules lie midway between the daughter chromo-somes among the interzonal fibrils (Fig. 25, c). During the ana-phase they become fewer and larger, no doubt by fusion with eachother. In the telophase the cleavage plane passes anteriorly tothem, thus leaving them invariably in the larger cell CD. So faras I could see, not one of them is left in the smaller cell. Fig. 29showing the mid-body of the first cleavage is a characteristic view Elementary Phenomena of Embryonie Development 203 of this stage, and shows with what certainty these granules may betraced into
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectzoology, bookyear1904
