. The development of the chick; an introduction to embryology . ^® ©si;- ks/S; Sf?)-^ •••i .a. er; ./.•• :r;^r ^;f^ :•.•: ^ 03. •;• ^••* ^ m • w•••• ^^ o o ■» ^ o o ^-^ o Ph ci P-t1—1 c *> O =3 S3 O -1^ c3 ^ to CO i:^ - ^ 5r P ^ ^ Utt. o o 2 fcJD ^M A O <D co e3 0) 1=1o o o is o^ -^ • fc£ GJ ^ ^1 S o a n =^ •^ .2 -*^ S -5 So2<< - o OQ DEVELOPMENT PRIOR TO LAYING 55 The margin of invagination is known as the Up of the blasto-pore or primitive mouth; the space between this margin andthe yolk is the blastopore, and the space between the entodermand yolk, derived from part of the subge
. The development of the chick; an introduction to embryology . ^® ©si;- ks/S; Sf?)-^ •••i .a. er; ./.•• :r;^r ^;f^ :•.•: ^ 03. •;• ^••* ^ m • w•••• ^^ o o ■» ^ o o ^-^ o Ph ci P-t1—1 c *> O =3 S3 O -1^ c3 ^ to CO i:^ - ^ 5r P ^ ^ Utt. o o 2 fcJD ^M A O <D co e3 0) 1=1o o o is o^ -^ • fc£ GJ ^ ^1 S o a n =^ •^ .2 -*^ S -5 So2<< - o OQ DEVELOPMENT PRIOR TO LAYING 55 The margin of invagination is known as the Up of the blasto-pore or primitive mouth; the space between this margin andthe yolk is the blastopore, and the space between the entodermand yolk, derived from part of the subgerminal cavity, is thearchenteron or primitive Fig. 27. — Diagrammatic reconstruction of the blasto-derm of which a longitudinal section is shown inFig. 26. C-D., Plane of Fig. 26. G. W., Germ-wall. 1, 2, 3, 4, 5, 6, and 7 indicateregions of the blastoderm which are approximately from1 to 7 cells deep respectively. The broken line around1 indicates the region where the blastoderm is approxi-mately one cell deep, x (After Patterson.) The first stage in the formation of the entoderm is interpretedas involution of the free margin, and this view is supported bythe fact, determined by Patterson, that the antero-posteriordiameter of the blastoderm is shorter than the transverse diameterduring this process, whereas previously the blastoderm wasapproximately circular. An even stronger support of this viewis furnished by experiments which demonstrate that injuries tothe margin made just prior to gastrulation appear later in an
Size: 1535px × 1627px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthorlilliefrankrattray187, bookcentury1900, bookdecade1910
