No. 2.] THE HYPOPHYSIS OF A MI A CALVA. 69 



actcristics of the cells are not enough different from those 

 described in the preceding stage to call for special remark. 



A comparison of sagittal with transverse sections (Fig. 17) 

 demonstrates that in shape the organ retains the general lentic- 

 ular form acquired early in its formation. It measures now 

 284 ft, in breadth by 88 /A in thickness. The lateral cartilages 

 (s/c.) have advanced far in towards the hypophysis, so that it 

 may be clearly seen that the organ lies in a distinctive space 

 surrounded by cartilages on all sides --the pituitary fossa. 

 Small bits of connective tissue may be seen between the 

 hypophysis and the brain in the folds of the former, and also 

 in the recesses between the lobes on the under side. The 

 infundibular base is folded more or less in conformity to the 

 lobing of the hypophysis. No evident communication between 

 the cavities nor ducts opening to the exterior have been 

 observed at this, the latest stage studied. 



A horizontal section of the hypophysis (Fig. 18) of a larva 

 about 20 mm. in length, thirty days old, shows that the lobing 

 of the organ is principally around the edge ; that its general 

 shape is circular in this plane, lenticular as a solid ; that a 

 cavity may be found near the end of each well-formed lobe, 

 which may possibly communicate with the central lumen by a 

 very narrow indistinctly defined channel ; that the cells are, 

 in general, arranged in a double row around each lobe, the 

 space between the rows constituting the channel mentioned ; 

 that the cells are arranged radially about the lumina. The 

 section figured is not exactly in a horizontal plane, but dips a 

 little posteriorly and to the right, so that the lobes mostly 

 appear to be on the anterior side, but are in reality of approxi- 

 mately the same number in each half. The organ is here seen 

 to be enclosed in the sella turcica, which is far advanced in 

 its formation. The infundibulum fits closely upon its upper 

 surface, the projections of the one fitting roughly into the 

 depressions of the other. No blood vessels can at this stage 

 be seen entering the organ, nor nervous tissue be found con- 

 necting it with the brain. It seems not to have become 

 glandular as yet. 



