8 AUGUSTUS G. POHLMAN 



been reported in connection with the condition of complete double 

 ureter (Johns Hopkins Bull., vol. 16, Feb. '04). 



TABULATION 



Tabulation of Material. + for transverse: = for sagittal: || for coronal. The 

 figures following indicate the thickness in microns. 



No. 1 (Mull 12; 2.1 mm.; +; 10; Good.) Modelled by Mall ('97). Allantois of 

 small lumen and in relation with the caudal border of the yolk sac. No evidences 

 of a cloacal membrane. 



No. 2 (Mall 391 ; 2.0 mm. ; + ; 10; Good). Appearance of hind gut. An inter- 

 val of several sections between allantois and yolk sac. No cloacal membrane. 



No. 3 (Mall 164; 3.5 mm. ; + ; 20; Good). Model A. X 100. Cloaca well devel- 

 oped and limited for caudal half of the ventral border by epithelial cloacal mem- 

 brane. Allantois comes off at right angles and at lower border of dermal navel. 

 Lateral furrow along later line of division. 



No. 4 (Mall 209; 3.0 mm. ; + ; 50; Fair). Relations about the same as the fore- 

 going stage. Sections too thick for detailed study. 



No. 5 (Mall 186; 3.5 mm.; +; 20; Good). Model B. X 100. Allantois wide 

 lumened and no distinct line of demarkation from the ventral cloacal segment. 

 Wolflian ducts have arrived but not as yet opened. Tail gut maximum of develop- 

 ment. Probably the first signs of cloacal division. 



No. 6 (Mall 87; 4.0 mm.; +; 20; Fair). About the same as the foregoing. 



No. 7 (Mall 148; 4.3 mm. ; + ; 10; Good X 100). Wolffian ducts open into cloaca. 

 Allantois of small lumen. Ventral cloacal segment widening. Evidences of di- 

 vision quite apparent. 



No. 8 (Mall. 76; 4.5 mm. ; + ; 20; Good). X 100. Widened ventral cloacal seg- 

 ment goes over indistinctly into allantois. Tail gut still quite large. Renal buds 

 well developed. With exception of large allantois and wider tail gut, quite simi- 

 lar to Model C. 



No. 9 (Mall 80; 5.0 mm; + ; 10; Good). Model C. X 100. About the same as 

 the foregoing stage. Tail gut undergoing degenerative changes. 



No. 10 (Mall 371; 6.6 mm.; = ; 10; Good). Tail gut rudimentary. Develop- 

 ment of cloaca and renal buds about the same as in no. 12. 



No. 11 (Mall 116; 5.0 mm. ; = ; 20; Good). X 100. Intracloacal epithelial plug 

 well marked. Stage about the same as that found in no. 12. 



No. 12 (Mall 2; 7.0 mm.; +; 15; Good). Model D. X 100. Marked develop- 

 ment of renal buds. Kidney and ureter segments evident. Ventral cloacal seg- 

 ment much widened. Allantois of narrow lumen. Intracloacal epithelial plug 

 marked. Tail gut maximum in length and slightly widened at caudal end. 



No. 13 (Mair241;6.0mm.; +; 10;Goo(l). Tailgutmore rudimentary than in 

 no. 12. Cloacal membrane wide and shows intracloacal epithelial ]>lug. Other- 

 wise about the same as in no. 12. 



No. 14 (Mall 383; 7.0 mm.; +," 10; Good). State similar to no. 12. Cloacal mem- 

 brane intact. 



No. 15 (Mall 397; 8.0 nma.; +; 10; Good). Similar to foregoing. 



