334 E. R. HOSKINS 



involving a relatively large portion of the side and roof of the 

 gut. The bulging is barely distinguishable on the external 

 surface, but is evident in sections. There is no thickening of 

 the epithelium in the anlage of the digitiform gland. 



In embryos of 19 mm. the area of evagination is more sharply 

 marked off from the rest of the gut and is relatively smaller. 

 It forms a shallow hollow bud (fig. 21) which projects laterally 

 from the intestine. 



The gland, once established, grows with rapidity, assuming 

 at first the form of a definite bud, and later becoming tubular 

 (fig. 22). In an embryo of 22.5 mm. it is 0.26 mm. long. The 

 distal extremity is turned anteriorly. The external surface 

 of the anlage is still smooth at this stage, with no indication of 

 secondary outgrowths. As the length of the gland increases 

 it pushes cephalad along the right dorso-lateral surface o the 

 intestine although touching that structure only at the proximal 

 end. 



Owing to the rapid growth of the proximal portion of the 

 gland, which later becomes the duct, and to the fact that the 

 distal portion does not move forward sufficiently rapidly to 

 keep the structure extended, the proximal part soon bends pos- 

 teriorly as seen in figure 23, of a 28.1 mm. embryo. In all 

 later stages the proximal part (or duct) of the gland first extends 

 backward and then bends anteriorly. In the 28.1 mm. stage 

 the posterior division of the gland is 0.20 mm. in length, or one- 

 fifth of the entire length of the gland. The outer surface of 

 the gland (fig. 27) has become irregular in outline, owing to 

 the beginning of primary tubule formation. 



In the 33.1 mm. stage (fig. 24) the proximal portion (or duct) 

 of the gland is shorter than in the 28.1 mm. embryo, being but 

 0.12 mm. long, but the entire length of the gland has increased 

 to 1.3 mm. The duct is bent sharply. The outer surface is 

 very irregular, owing to the great increase in the number of 

 primary tubules, which are actually smaller than in the pre- 

 ceding stage (fig. 28). They have assumed various shapes, ow- 

 ing to crowding, but most of them are flattened at the periph- 

 ery from the pressure of the capsule. Some of the tubules 



