LIFE HISTORY OF DESMOGNATHl> I-TSCA. 



279 



between the many irregular folds of the lining mucous membrane. 

 The cells of the mucous membrane are sub-columnar in form, 

 with a smooth exposed surface. The final stages of this histo- 

 genesis must take place with great rapidity, during the last few 

 days before hatching. In the 13 mm. embryo neither folds, 

 ciliated cells, nor glands of any kind have appeared in the 

 alimentary canal; the stomach is differentiated from the cesoph- 



13 c 



13d 



k 



FIG. 9. A series of dissections of the alimentary canals of various stages of 

 Desmognathus fusca, showing the gradual consumption of the yolk and the dif- 

 ferentiation of the intestine, (a) terrestrial larval stage B, 3 days old; (b) same 

 stage as (a) with the liver removed; (c) terrestrial larval stage!?, 7^ days old; (d) 

 terrestrial larval stage F, 15^ days old; (e), (/), (g), (h), aquatic larval stages col- 

 lected in September and October; (i) aquatic larval stage collected in May; (k) 

 adult stage, length 45 mm. 



Lines 130, 136, I3C, and i$d show the levels and directions of the respective 

 sections of Fig. 13; bl, bladder; du, duodenum; gbl, gall bladder; in, intestine; 

 /, liver; p, pancreas; st, stomach; sp, spleen; r, rectum; y, yolk mass. Drawn with 

 Abbe camera. X 4. 



agus, only in being less flattened dorso-ventrally, and con- 

 taining in its cells a larger amount of yolk; there is an enormous 

 amount of mitosis in progress especially in the cesophageal 



