DEVELOPMENT OF THE HYPOPHYSIS 439 
-48 mm. embryo the ridge is very distinct and the connection 
of the lumen of this part with the lumen of the anterior lobe has 
become constricted. The constriction forms the narrowed con- 
nection of the inferior sacs to the anterior lobe. As previously 
stated, the growth of the furrows separating the inferior sacs from 
the lateral sides of the anterior lobe is well marked at this time. 
A sagittal section of the hypophysis of a 50 mm. embryo shows 
a short interhypophyseal canal (fig. 9). In a 95 mm. embryo 
the canal has lengthened considerably. The walls are composed 
of one or two layers of low columnar cells. In the pup the canal 
is longer than in the embryos but the diameter is about the same 
as In younger specimens. In: the adult the canal has increased 
- in length and diameter and is attached in the floor of the anterior 
TABLE 4 
Showing the size of the interhypophyseal canal 
SIZE OF SPECIMEN ane oo, ec Pathe este CANAL 
Embryo of 50:mm....0...5..... . 0.13 0.042 
OD sma swisee es ote: 0.36 0.048 
Teta kee AE See 0.44 bs 0.048 
BROUMRS S ccs MAE Boch atts, Gt, os 0.68 0.080 
lobe at or near its caudal end. Its other attachment is near the 
dorsal side of the connection between the inferior lobes. There 
are no tubular outgrowths from it such as Haller found in Mus- 
telus. Table 4 shows the size of the canals at different stages. 
It will be seen that there is a continual increase in the length of 
the canal. The diameter in the older specimen is somewhat 
greater than in the 50 mm. embryo, although there is no great 
change. A distinct lumen is present. In the median line 
there is a well defined layer of connective tissue extending from 
the tip of the parachordal plate (fig. 9) forward to the floor of 
the anterior lobe of the hypophysis. This layer develops rapidly 
after the canal is formed and surrounds it. It is well defined in 
a 50 mm. embryo, but becomes thicker in the adult. This layer 
separates the inferior lobes from the rest of the hypophysis and 
JOURNAL OF MORPHOLOGY, VOL. 26, No. 3 
