444 E A. BAUMGARTNER 
ADDENDUM 
After the completion of the present work a paper by M. W. 
Woerdeman: ‘‘Vergleichende Ontogenie der Hypophysis”’ ap- 
peared (Arch. f. mikr. Anat., Bd. 86). This investigator figured 
Rathke’s pouch in an 8 mm. Torpedo embryo. In somewhat 
older embryos (12-15 mm.) the region where Rathke’s pouch 
opens into the mouth evaginates and in still later embryos a 
region anterior to this is constricted from the mouth. The 
hypophysis then consists of a small Rathke’s pouch somewhat 
constricted from an anterior (ventral) ‘Mittelraum’ and anterior 
to the latter, the ‘Vorraum.’ The middle division, in 20 mm. 
embryos, divides by a circular constriction into a dorsal and a 
ventral part. In this way the ventral sacs are formed. The 
hypophyseal stalk now opens into the ventral sacs, in which 
observation Woerdeman agrees with that of Gentes and Sten- 
dell. According to Woerdemann’s comparison of the parts of 
the hypophysis with those described by Stendell, Rathke’s ~ 
pouch is homologous with the superior lobe (table 1, p. 400) 
and the ‘Mittelraum’ and ‘Vorraum’ are homologous with the 
anterior lobe. The ventral sacs and lateral lobuli which he 
described are probably homologous with the inferior lobes. In 
Squalus I have described Rathke’s pouch, or the early anlage of 
the hypophysis as giving rise to the caudal extremity of the 
anterior lobe. A later evagination ventral to this gives rise to 
the middle portion and anterior extremity of the anterior lobe. 
The secondary evagination is early recognized, as the epithelium 
here is thickened (page 408). The opening from the mouth 
to the early hypophyseal anlage, or Rathke’s pouch, secondarily 
comes to open in the later evagination (page 410) of which there 
is only one in Squalus. The inferior lobes and the superior lobe 
develop from the early hypophyseal anlage in Squalus, as has 
been described (pp. 410-11). The hypophyseal stalk is not 
constricted from the anterior lobe with the developing ventral 
lobes but remains connected with the caudal wall of the middle 
portion of the anterior lobe until it disappears. 
