45r> 



M 



R. F. E. BEDDARD ON HAPALEMUR GRISEUS. [JuilC 16, 



We must undoubtedly regard this bloodless fold of membrane — 

 the frenum — as Mr. Treves^ has pointed out, as being the true 

 mesentery of the caecum, and the development of the lateral folds 

 as an entirely secondary process. 



Looking at the matter from this point of view Hapalemur is 

 evidently, wlien compared with Lemur, a specialized type. It is 

 not, however, so easy to decide whether the Lorisinse or the 

 Lemurinse include the older types. Perhaps the ])fesence of two 

 lateral folds in the Lorisinse is evidence of a more speciahzed con- 

 dition than is shown by either the Lemurinas or Galagininse, where 

 only one is developed. On the other hand, the independence of the 

 frenum and the lateral fold in Loris and the Potto, as contrasted 

 with their fusion in Lemur (also, however, in Nycticebus), might be 

 used as an argument on the other side. 



There can, however, be no doubt, and that is rather the point 

 upon which I wish to dwell in the present communication, that 

 Hapalemur is so far a speciahzed type of Lemur in that it has lost 

 the true mesentery of the caecum. Whether this is, or is not, 

 correlated with the altered form of the caecum itself is not a matter 

 of importance, since in any case the organ itself shows a departure 

 from the ordinary Lemurine caecum in its shape. 



Srain. 



The brain was carefully extracted, and is in an excellent state of 

 preservation. In the hardened brain I have made the following 

 measurements, which are j)laced side by siile with corresponding 

 measurements of well-preserved brains of Lemur anjuunensis and 

 Galago crassicaudatus. 



From these measurements it follows that the brain of Lemur is 

 broader as well as deeper than that of Hapalemur, that the brain of 

 Galago is broader but shallower than that of Hapalemur, and that 

 the brain of Lemur is just perceptibly broader but considerably 

 deeper than that of Oalago. 



The narrowness of the brain of Hapalemur, as contrasted with the 

 other types used for comparison, is indeed apparent to the eye with- 

 out making accurate measurements to prove it. 



As will be also seen from the above table, the difference in length 

 between the brains of Hapalemur and Galago is very small ; the 



' " The Anatomy' of the Intestinal Canal and Peritoneum in Man." Hun- 

 torian Lecture, 18S5. London, 1885. 



