486 
J. GRAHAM KERR. 
differentiated from tlie larger hinder region (mid-gut and 
hind-gut) which forms the main storehouse for the yolk. 
The commencing development of the fore-gut is illustrated 
by text-fig. 1 A, in which the fore-gut rudiment is beginning 
to be nipped oft' from the rest of the endoderm by the de- 
velopment of a chink beneath it. This chink then gradually 
spreads backwards, as shown in text-fig. 1 B, and also later- 
ally, and in this way the fore-gut becomes demarcated, the 
Text-fig. 2. 
Section through junction of fore- and mid-gut of a Lepidosiren 
larva of stage XXXIV, showing the origin of the pyloric valve, 
c. 9)1. g. Cavity of mid-gut. /. g. Hind end of fore-gut. 
ventral part of the space alluded to becoming occupied by the 
pei’icardiac cavity with its mesodermal lining. The folding 
off of the fore-gut is continued backwards until, about stage 
XXXII, it reaches the level of the pylorus, after which it 
increases in length by its own growth, and undergoes gradual 
histological differentiation until the adult condition is reached. 
About stage XXXIV the active growth in length of the fore- 
gut causes it to push its hinder end into the cavity of the 
raid-gut, the wall of which is relatively thin at the point of 
junction of fore- and mid-gut (see text-fig. 2). The 
flattened spout-like projection of the hinder end of the fore- 
