Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . the primitivestreak, and lies in the line of the long axis of the germinalarea, which itself lies in the transverse axis of the egg (fig. 325, a).Under the nota primitiva, the cumulus proligerus, deeply seated,may still be seen very plainly glistening through (fig. 326, A, B, d). The nota primitiva rises slightly above the level ofthe germinal area (fig. 326, b) ; it is thicker and blunter ante-riorly, or towards that end which becomes th
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . the primitivestreak, and lies in the line of the long axis of the germinalarea, which itself lies in the transverse axis of the egg (fig. 325, a).Under the nota primitiva, the cumulus proligerus, deeply seated,may still be seen very plainly glistening through (fig. 326, A, B, d). The nota primitiva rises slightly above the level ofthe germinal area (fig. 326, b) ; it is thicker and blunter ante-riorly, or towards that end which becomes the head of theembryo, thinner, and tending to a point posteriorly. The notaprimitiva is probably the groundwork of the brain and spinalcord. [§ 484. The nota primitiva, an aggregate of dark granules in the first instance, becomesmore fluent by and by, andpresents itself as a layer of de-licate, transparent masses, bythe side of which, between thesixteenth and eighteenth hour,a pair of new formations arisesymmetrically, near the mid-dle line. These are the lami-nce s. plicfB dorsal esâthe dor-sal laminae, two cylindricalrolls or enlargements, which. B Fig. 326.âIdeal sections of (after Baer, with slight varia-tions).âA, transverse section ; B,longitudinal section ; a, vitellinemembrane, indicated by a finelydotted line ; b, nota, or primitivestreak, with the serous layer of the arise parallel to the nota primi-tiva, and form a couple of cris- tse, or ridges, one on either. , â ., 9~ 00- -⢠Qr>o , Slde, of lfc (%s- 327 and 32f blastoderma, corresponding to the &, »), which diverge anteriorly area pellucida; c, mucous layer of and posteriorly, being nearest the blastoderma, corresponding to about the middle of their the area vasculosa; d, cumulus pro- len«th an^ sloping somewhat hgerus s. nucleus cicatncuke. â .,, ^ from without inwards, or to-ward? one another. The angles of the ridges are softlyrounded off; each ridge has the appearance of a clear broa
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
