1905.] ox THE EXCEPHALIC ARTERIAL SYSTEM IX SAUROPSIDA. 59 



and gave rise to " rosette-stages," about 2"5 ju to 3'5 /,< in diameter. 

 A ''rosette" consisted of a schizont dividing up into merozoites. 



This parasite was probably the smallest Hasmogregarine yet 

 described, and it occurred in large red blood-corpuscles, those 

 of Triton cristatus being about 30 fx in long diametei\ The 

 reseai'ch on this parasite and allied foi'ms was being continued. 



The following papers were read 



1. A Contribution to the Knowledge of the Encephalic 

 Arf:erial System in Sauropsida. By Frank E. Beddard, 

 M.A., F.R.S., Prosector to the Society. 



[Received Marcli 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, Testudo 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 oifered 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 q/'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 Iguana. The 

 postei'ior pair of cerebellar arteries arise, as in Iguana, from the 

 basilar artery at the middle of the medulla, and are larger than 

 the anterior pair, which arise from the fork of tlie basilar in front. 

 This fork is not quite so symmetrical as in Iguana. The left side 

 and the left carotid are rather thicker than the I'ight, 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 Iguana ; but the large size of the 

 ophthalmic arteries is a point of likeness to Python. 



* De sj'stemate vasovum Fsaminosatiri grisei. 1853. 



