Henry L. Bruner 41 
the oral mucous membrane and to the upper jaw, and the two anasto- 
moses, one behind the rostrum, the other in front of Jacobson’s organ, 
are common to both vessels. It seems probable, therefore, that the an- 
terior part of the vena maxillaris of the snake has been derived from the 
sinus palatinus lateralis of saurian ancestors. The anterior part of the 
vena maxillaris of the lizard seems to be represented in the snake by the 
vena nasalis externa ventralis, whose relation to the vena rostralis may 
be explained by obliteration of the posterior part of the maxillary vein. 
The orbital part of the vena maxillaris of the snake might be derived 
either by median migration of the vena maxillaris of the lhzard or by a 
dorsal migration of the sinus palatinus lateralis. The postorbital part 
of the vena mavxillaris of the lizard has probably been obliterated. 
8. The cephalic veins of lizards, snakes, and turtles are connected by 
numerous anastomoses, especially in the adult stage. These anastomoses 
are for the most part open passages, permitting the movement of blood 
in either direction. They apparently serve to equalize the blood-pressure 
in different parts of the head. 
9. The most striking characteristic of the venous system of the Sauria, 
Ophidia, and Testudinata is the abundance of blood sinuses in the head. 
These include not only intracranial sinuses, similar to those of other 
vertebrates, but also extracranial sinuses which probably do not occur 
elsewhere in the vertebrate series. The significance of these extracranial 
sinuses will be considered in the second part of this paper. 
PAK SECOND: 
ON THE SIGNIFICANCE-OF THE CEPHALIC SINUSES OF THE 
SAURIA, OPHIDIA, AND TESTUDINATA. 
The extraordinary development of blood sinuses in the head of the 
Sauria, Ophidia, and Testudinata suggests a lacunar blood system, such 
as we find in many invertebrate animals. The resemblance is a super- 
ficial one, however, for the reptilian sinuses are formed during embry- 
onic life by the enlargement of veins and capillaries. Moreover, they 
are limited in their distribution to the cephalic region and, therefore, 
their existence must be explained by a study of local conditions. 
An investigation of the cephalic sinuses of the Reptilia was suggested 
several years ago by certain preliminary studies on the ejection of blood 
by Phrynosoma. In order to explain this phenomenon it seemed neces- 
sary to assume a temporary increase of blood-pressure in the region of 
