440 E. A. BAUMGARTNER 
makes their dissection difficult. The cells and fibers in it are 
arranged concentrically around the canal. In the adult, the 
layer of connective tissue is still prominent and extends the entire 
length of the canal. 
Fig. 40 Transverse section of the hypophyseal stalk of a 28 mm. embryo. 
(H.E.C. Series 1357). X 350. 
Fig. 41 Transverse section of the hypophyseal stalk of a 33 mm. embryo. 
(H:E.C. Series 307). X< 350. 
” 
4. Development of the hypophyseal stalk 
The stalk connecting the hypophysis with the mouth is formed 
in 22 to 24 mm. embryos. It is present in one 21 mm. embryo 
which shows the anterior end constricting from the mouth. 
In these stages it is oval in cross-section, the lumen is very large, 
and its walls are formed of a layer of low columnar cells, the nuclei 
of which are somewhat elongated and contain considerable 
chromatin. In the posterior (superior) margin are found many 
yellow pigment granules, as has been described by Hoffmann 
(86). These granules are found within the cell, sometimes 
apparently in the nucleus (fig. 32). As Hoffmann stated, they 
are first seen in the bucco-pharyngeal membrane, but later 
occur also in the wall of the stalk. Miller (71) had described 
them in the stalk in Acanthias embryos of 30 mm. length. 
In 28 mm. embryos the lumen in the stalk is small. The wall 
consists of a double layer of epithelial cells, the outer of which 
