. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MICRODISSECTION STUDIES. 345 nation they were pinched off from the cortical portion of the eggs. None developed of those which were separated in such a way that there was no question as to their lacking any of the original cortex of the egg. An endoplasmic sphere, in order to develop at all, apparently must incorporate in its substance at least a part of the original cortex of the egg. This is shown in Fig. 27. An exovate was. 3. IS FIG. 27. a, an exovate is produced l}y squashing and most of the ecto- plasmic part is
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. MICRODISSECTION STUDIES. 345 nation they were pinched off from the cortical portion of the eggs. None developed of those which were separated in such a way that there was no question as to their lacking any of the original cortex of the egg. An endoplasmic sphere, in order to develop at all, apparently must incorporate in its substance at least a part of the original cortex of the egg. This is shown in Fig. 27. An exovate was. 3. IS FIG. 27. a, an exovate is produced l}y squashing and most of the ecto- plasmic part is cut away along line of arrow, b, the endoplasmic sphere formed itself incorporating a small part of the cortex. Upon fertilization the small cortical region formed a partial fertilization membrane, c, many furrows form simultaneously over the surface of the egg showing that it has been fertilized. (Note that the small cortical piece to one side of the egg has segmented in two.) d, the egg has reverted into a multinucleated nonseg- mented mass except for three blastomere-like bodies which were pinched off. e, the fragment is again attempting to segment. produced by crushing an egg (Fig. 27-0). However, before the exovate was set free most of the cortical remnant was cut away, leaving a very small piece which was drawn into the circumference of the endoplasmic sphere. On being inseminated a small shred of the egg membrane lifted off from this remnant, and this was all that constituted the fertilization membrane (Fig. 2/-&). A sperm on entering this sphere underwent nuclear division several times. This was followed by cleavage furrows which formed on the surface of the egg between the peripheral nuclei and gave to the egg the appearance of a mulberry (Fig. 2/-c). Some of the furrows deepened sufficiently to pinch off nucleated bodies. A few minutes later the furrows became obliterated and the main body of the egg appeared again as a non-segmented but multi- nucleated mass (Fig
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
