John Warren 21 
ular number of vesicles attached to the brain by a narrow opening. Ac- 
cording to Kingsbury (21) the structure in Necturus consists of an 
aggregation of closed vesicles, forming an oval, flattened body, and there 
is no connection with the brain. The cavity of the epiphysis commun- 
icates through its stalk with the cavity of the diencephalon up to 15 mm., 
when the cavity in the stalk becomes obliterated. The stalk persists and 
was present in all the adult brains which I examined, but in some cases 
it was so small that it could easily be overlooked. The reconstruction 
of an adult epiphysis, Fig. 22, shows that the cavity of the organ forms 
a large chamber subdivided to a certain extent by incomplete septa. A 
much more solid area is seen towards the caudal extremity, which is 
placed just over the stalk. The same characteristics I have observed in 
another model made from a different brain. One gets the idea that the 
epiphysis consists of a series of vesicles in studying sagittal sections a 
little to one side of the median line, as for instance in Fig. 17, where the 
epiphysis was displaced a little to one side. 
. There has been such a vast amount written on the origin of the 
epiphysis and the pineal or parietal eye and their homologies that it seems 
superfluous to add anything more here. In a very general way, however, 
there seems to be some sort of proportion in the relative development of 
the paraphysis, epiphysis, and the parietal eye. In urodela where there 
is no parietal eye and a small epiphysis, the paraphysis reaches its highest 
degree of development. In those forms where the paraphysis is rudi- 
mentary or relatively slightly developed the parietal eye is present or 
else the epiphysis is relatively highly developed. Compare, for example, 
the figures of Burckhardt (3) of Petromyzon, Minot (28) of Acanthias, 
Burckhardt (3) of Trout, Leydig (26) and Voelzkow (38) of reptilia, 
and Dexter (5) of the fowl. Rana, however, seems to be a marked ex- 
ception to this statement, as there the paraphysis, epiphysis, and pineal 
eye are all present and well developed, and the same may be said for 
Lacerta (Francotte, 10 and 11) and Sphenodon (Dendy, 6). As the 
paraphysis and epiphysis are glandular structures they have probably 
some sort of compensatory function and where one is highly developed 
the other is relatively rudimentary or even absent. Compare in this 
respect also Torpedo with Acanthias and the crocodile and alligator with 
the chick. 
As a rule the stalk of the epiphysis is placed immediately caudad to the 
supra commissure, in all cases I believe, except in the toad, where there 
is a distinct interval between it and this commissure (Sorenson, 36). 
In Necturus there is an interval in the roof of the brain between the stalk 
and the posterior commissure. This portion of the roof of the brain was 
