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From Embryology

Table I. Table showing extent of cloacal membrane relative to the size of the embryo

Embryo Length of embryonic disc Presomite Cloacal membrane
W.O. (V. Mollendorlf, 1925) 0.25 mm What von Mollendorlf describes as the cloacal membrane is, according to Florian, the primitive streak, and von Mollendorif’s allantois is the cloacal membrane of Florian
“Fetzer” (Fetzer & Florian, 1930) 0.26 mm. The cloacal membrane is separated by an interval from the primitive streak
T. F. (Florian (1928)) 0.4 mm The cloacal membrane is a cord of cells which extends on to and connects the allantoic endoderm with the amniotic ectoderm
Bi I ? Primitive streak reaches the cloacal membrane
Bi 24 0.625 mm Length 0-06 min
“Hugo” Stieve (1926) 0-635 mm Length 0-035 mm
“Beneke” 0.75 mm Cloacal membrane separated by an interval from (Strahl & Beneke, 1910) the primitive streak
W.A. 17 (Grosser, 1930-1) 0.85 mm Length 0-13 mm and extends on to the allantois
“Dobbin” (Hill & Florian, 1931) 0-98 mm Length 0.08 mm
Peh-Hochstetter Rossenbeck (1923) 1-4 mm Cloacal membrane extends well on to allantois
Heuser (1930) 1.6 mm Cloacal membrane extends well on to allantois
Ingalls (1918) 2-0 mm Length 0-12 mm, and there is an additional connexion between the allantoic endoderm and amniotic ectoderm
Somites
F. von Orts Llorca (1934) 2 Cloacal membrane in two parts—one of which is allantoic
H 3 (Wilson) 2-3 Cloacal membrane at the commencement of allantois
Bi II 4 Cloacal membrane broken up—one portion involvingallantois
Sternberg (1927) 4 Cloacal membrane is in four portions
Pfannenstiel-Kromer 5-6 Very short cloacal membrane extending some distance into the allantois
Dandy (1910) 7 Not mentioned
Payne (1925) 7 Not mentioned
West (1930) 8 Length 0.09 mm
Etemod (1899) 8 Length 0-05 mm
Corner (1929) 10 Cloacal membrane terminates before reaching the allantois
Embryo Bl. XI 10 Cloacal membrane terminates before reaching the allantois
Pfannenstiel III 13-14 Has trebled its length compared to P£annenstiel-Kramer
Heuser (1930) 14 Length 0-18 mm
Atwell (1930) 17 Length 0-18 mm Extends to the allantois
Davis (1924) 20 Length 0-16 mm


Table I is a series of embryos arranged according to size, with, as far as can be obtained, the available data regarding the cloacal membrane.