DEVELOPMENT OF DIGIT1FORM GLAND 



355 



Figs. 15, 16, 17, 18, and 19 X 50. Sections through the middle of the occluded 

 portion of the post-valvular intestine in Acanthias embryos. 

 Fig. 15 Embryo 28.1 mm. in length. 



Fig. 16 Embryo 33.1 mm. in length. 



Fig. 17 Embryo 47.5 mm. in length. 



Fig. 18 Embryo 95 mm. in length. 



Fig. 19 Embryo 200 mm. in length. 



Ep., epithelium in solid black; R.D. 



solid ridge which is continuous with the solid end of the duct of the digitiform 

 gland (fig. 13); R.S., solid ridge which is continuous with the intestine posterior 

 to the occluded portion and which splits later to form the new lumen (fig. 13). 

 Note the very small lumen in figure 15. The areas of connective tissue within 

 the epithelium in figure 17 are continuous at a different level with that external 

 to it, 



