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Updated: May 24, 2025
The nucleus segmented and migrated into that part of the superficial cytoplasm which remained alive, and this proceeded to develop that particular part of the embryo to which it would have given rise if the rest of the egg had not been killed. There was no regeneration of the part killed, no formation of a complete embryo. It may be pointed out that segmentation in the insect egg is peculiar.
It soon becomes cloudy, while remaining diaphanous at each extremity. Fine lines, hardly perceptible to the most penetrating lens, show themselves in transverse circles. These are the first signs of segmentation. A contraction appears in the front hyaline part, marking the head. An extremely thin opaque thread runs down either side.
We have the old argument from embryonic transformism brought forward without any hint that later investigation tends to show differentiation further and further back, prior to segmentation and, according to some, in the very protoplasm itself.
"The organs of the body are formed in the sequence of their organic importance; the most essential always appear first. "Thus, in Fishes, the first changes consist in the segmentation of the vitellus and the formation of a germ, processes which are common to all classes of animals.
The essential thing is and remains what was in the cell. Through gemmation, differentiation, segmentation, evolution, or whatever other technical expressions we may use for division, multiplication, budding, increase, etc., each cell became a hundred, a thousand, a million.
He is still inside his chemico-physical explanation to begin with; and, even within that, he still leaves us anxious for the explanation of a number of points for example, as to the nature of the chemical process which accompanies, or is the cause of, segmentation. We in no way press these questions; for similar demands could be made in so many cases; we only indicate that they are there.
The Potawattamies have eight gentes of the same name with eight among the Ojibwas, while the former have six, and the latter fourteen, which are different, showing that new gentes have been formed in each tribe by segmentation since their separation.
It is important to know the simple manner in which this organization springs up, and the facility with which it is managed as a part of the social system of ancient society. With the increase of numbers in a gens, followed by local separation of its members, segmentation occurred, and the seceding portion adopted a new gentile name.
Thus far this process of segmentation is similar to that of the egg in other animals; but, as we shall see hereafter, it seems usually to result only in a change in the quality of its substance, for the portions coalesce again to form one mass, from which a new individual is finally sketched out, at first as a simple embryo, and gradually undergoing all the changes peculiar to its kind, till a new-born animal escapes from the egg.
To understand the nature and origin of these protozoa-colonies we need only follow step by step the first embryonic products of the stem-cell. In the genealogical tree of the Vertebrates this palingenetic form of segmentation has been preserved in the Amphioxus alone, all the other Vertebrates having cenogenetically modified forms of cleavage. Original or primordial ovum-cleavage.
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