18 Paraphysis and the Pineal Region in Necturus Maculatus 
choroid plexus that it is not astonishing that it was at first regarded as 
a portion of this plexus. According to Minot (28) the paraphysis of 
Rana is characterized by the character of its epithelium, its tubular struc- 
ture and its apparently sinusoidal circulation. This is practically similar 
to the conditions found in Necturus. 
In Menopoma Sorensen (36) describes the paraphysis as a solid vas- 
cular mass, and in Ichthyophis Burckhardt (3) describes it as an 
elaborately folded structure of a glandular character. In Amblystoma, 
Kycleshymer (8) shows that the organ gives off tubules and has a digit- 
ated appearance. In Diemyctylus (Mrs. Gage, 13), in an embryo of 
10 mm. the paraphysis closely resembles that of Necturus at 18 mm. 
(Minot, 28, Fig. 13), and in the adult it is a long tube giving off many 
tubules in close relation to vessels. 
Herrick (15) calls the paraphysis of an adult Necturus the “ pre- 
paraphysis ” and says it consists of an irregular central chamber with 
complicated diverticuli in close relation to vessels. This description 
corresponds closely with Fig. 17. The model of the adult paraphysis, 
Fig. 19, shows the complicated arrangement of the tubules, many of 
which anastamose with each other, and the spaces between the tubules 
are filled by blood-vessels. 
Fig. 6 shows how the paraphysis at 12.5 mm. is beginning to invade a 
large vessel lying over it on the surface of the brain. This vessel at this 
point is much enlarged. Fig. 10 shows this relation much clearer and 
also that these vessels in relation to the paraphysis are tributaries of the 
internal jugular vein. Fig. 15 shows the relation of the paraphysis to 
these vessels at 26 mm. and that the vessels pass into the choroid plexuses 
both dorsad and ventrad to the organ. The little tubules can be seen grow- 
ing out into the vessels. Fig. 17 shows how these relations between vessels 
and tubules in the adult become much more intimate, and the vessels 
corresponding to those in Fig. 15 are seen passing into the choroid plex- 
uses dorsad as well as ventrad to the paraphysis. Schdbel (33), who 
studied the circulation in the brain of certain amphibia, of which 
Necturus was one, shows that in the adult two large vessels pass outward 
just caudad to the hemispheres to empty eventually in the internal 
jugular vein. These vessels surround the paraphysis and anastomose 
with two or three large vessels running forward between the hemispheres. 
This is practically the same arrangement shown in the model in Fig. 10. 
He does not mention the paraphysis but refers to it as a large venous 
plexus. Rex (32) also has studied the veins in the amphibian brain, 
and his preparations are practically the same as Schobel’s. He refers 
to the paraphysis as the “ nodus chorioideus ” and says that it is a sort 
