1905.] ON THE ENCEPHALIC ARTERIAL SYSTEM IN SAUROPSIDA. 59 
and gave rise to “rosette-stages,” about 2°5 p to 3°5 jin diameter. 
A “rosette” consisted of a schizont dividing up into merozoites. 
This parasite was probably the smallest Hemogregarine yet 
described, and it occurred in large red blood-corpuscles, those 
of Triton cristatus being about 30, in long diameter. The 
research on this parasite and allied forms was being continued. 
The following papers were read :— 
1. A Contribution to the Knowledge of the Encephalic 
Arterial System in Sauropsida. By Frank E. Bepparp, 
M.A., F.R.S., Prosector to the Society. 
[Received March 29, 1905. | 
(Text-figures 16—21.) 
The following pages contain some facts relating to the principal 
vessels of the arterial system of the brain in a number of Lizards, 
in a Python, and in the giant Tortoise, Zestudo vicina. Some of 
these have not been hitherto studied; some have been examined 
by Rathke and others, and references to these anatomists will be 
found in the proper place. Most of the brains which I describe 
are now in the Museum of the Royal College of Surgeons. My 
principal object has been, next to the recording of new facts, to 
ascertain how far the characters offered by the distribution of 
these vessels, which are undoubtedly of use in the systematic 
arrangement of mammals, are also of use in the remaining 
Vertebrata for a like purpose. 
§ Brain of Varanus exanthematicus. 
Although the cerebral arterial system of Varanus griseus has 
been described by Corti*, I have a few notes to add to his 
description and comparisons to make with the other genera treated 
of in the present communication. 
The two vertebral veins are strong and mark the posterior end 
of the medulla, precisely as is the case with Jguana. The 
posterior pair of cerebellar arteries arise, as in /gwana, from the 
basilar artery at the middle of the medulla, and are larger than 
the anterior pair, which arise from the fork of the basilar in front. 
This fork is not quite so symmetrical as in Jguana. ‘The left side 
and the left carotid are rather thicker than the right, and there 
is thus a suggestion of the marked inequality of these arteries in 
Python. The branches to the corpora bigemina and to the rest of 
the brain are quite as in /guana; but the large size of the 
ophthalmic arteries is a point of likeness to Python. 
* De systemate vasorum Psammosauri grisei. 1853. 
