502 ALELS. [VoL. XII. 
p. 203) as the homologue of the eyestalk in selachians, and that 
part of it that lies under the base of the brain, behind the hypo- 
physis, is the “hintere Quer-Anastomose”’ of Gaupp in Anguis 
and Lacerta (No. 41, p. 571). The transverse anastomosis in 
Anguis and Lacerta lies above the hind end of the hypophysis, 
between it and the base of the brain, but as the hypophysis in 
Amphibia grows backward from its point of attachment to the 
gut (No. 71, Figs. 6 and 7), and in Ganoids forward (No. 69, 
Figs. 13-16), this difference of position of the vein is probably 
apparent rather than real. In larvae of Acipenser a vessel that 
has, in the median vertical plane of the head, exactly the position 
of the vein vo in larvae of Amia is considered by von Kupffer 
(No. 69, p. 11) as the artery of the mandibular arch. It may 
be such in Amia also, the choroid gland representing the de- 
generated respiratory organ of that arch, as has been suggested 
by Dohrn, I believe, though I do not find the reference. The 
artery disappears in older larvae of Acipenser (No. 69, p. 25). 
The base of the brain in Amia, above and in front of the 
transverse anastomosing vein vo, is, in 50 mm. specimens, flat 
and thin, with a large, median, much-plaited fold projecting into 
the cavity of the infundibulum. At the middle of its length the 
lateral edges of the fold almost touch, leaving a slit-like opening 
into its relatively large interior, which is filled in sections with 
what is apparently glandular tissue and a dense mass of blood 
corpuscles. Immediately below and in front of the fold, and 
hence immediately under and in contact with the base of the 
brain, is the hypophysis, a flattened oval mass of tissue similar 
to and continuous with that that fills the fold. It is as wide 
as the underlying hypophysial fenestra, is everywhere separated 
from the mouth cavity by the parasphenoid, and is everywhere 
limited and defined by membrane excepting toward the brain 
and where it comes in contact with the vein vo, at its posterior 
end and along the posterior portion of its lateral edge. At 
these places the tissue of the organ is apparently directly con- 
tinuous with masses of blood corpuscles in the vein. The 
saccus vasculosus begins behind the vein, and in its posterior 
portion ramifications of the central cavity give to it a glandular 
appearance. 
