MOEPHOLOGT OF THE T5RAIN IX THE MAMMALIA. 335 



possibility of these differences having any specific value is Beddard *. His remark that 

 "the bigger brains are on the whole more complex than the smaller" may seem a mere 

 truism; but I have found some noteworthy exceptions to it. Tlius one of the simplest 

 Lemur's brains I have seen Avas also l)y far the biggest : it belonged to a Lemur variiifi 

 and weighed 39 grammes, its cerebral hemispheres being each It) mm. long and 21-") 

 mm. broad ; it had no fronto-orbital sulci, very poorly developed orbital and collateral 

 sulci, and unusually short lateral, parallel, and .straight sulci (fig 3). 



My examination of crania bears out llio statement of Beddard that the variety 

 nnjuanends has the simplest brain of all members of the genus. It is the only brain in 

 Avhich no trace of the sulcus / is found. But with this (possible) exception, all of 

 Beddard's remarks on supposed specific characters are the mere record of individual 

 variations, every one of which may occur in any species. 



So far as my ob.servations go, it is quite impossible to assign any specific value to the 

 A-ariatious. But this may possibly be due to the fact that an insufficiently large number 

 of brains was available for examination. As the variations are practically AvhoUy confined 

 to the external aspect of the hemisphere, the investigation necessary to settle this 

 question can most readily be carried out on a series of skulls, from A\hich we can readily 

 de,termine the size, shape, and pattern of the sulci ia tlie cerebral hemisphere. 



Concerning the exact size and shape — /. c chiefly the amount of cerebellum ovei-lapi)ed 

 — there are only very scanty data. 



Max "Weber records the brain-Aveights of two specimens of Lemur variiis, Geoff. ; that 

 of a male 33 grms., being x^ of the body-Aveight, and that of a female 287 grms., being 

 tV of the body-AA^eight. A representative of this species died in the Ghizeh Zoologicjil 

 Gardens, and I found its brain-weight to be 39 grnis. and its body-Aveight 2900 grms., 

 ■i.e. the brain Avas J.f of the body-weight. 



Max Weber also records the weight of the 1-raiu and its relation to the body-weio-ht 

 in two females of Z^W7?;- moiifjo:, L., as 28 (-^;) and 21-1 (,;iy) respectively. The only 

 other records of brain-Aveights by Ziehen, Flarau and Jacobsohn, are of little A^alue, 

 because they refer to s])ecimens the Aveights of Avliich were altered by the action of 

 reagents. I have found tliat the extent of tiie area of CL'rebellum uncoA-ered by the 

 cerebral hemisphere is subject to variation. It A\as largest m a brain of Lemur carlu^ 

 (fig. 3), but, as I have found tlie extreme types of variation in the brains of two 

 specimens of Lemur fulrun (which died in the same Aveek and were examined under 

 exactly similar conditions), it does not seeni possible to attach any specific importance 

 to this fact. (Compare figures 6 and 7, also figures 1, 2, and 3.) 



With regard to the variations in the uieasuiements of the hemisphei'es, my data arc 

 A'orv scantA". 



Flatau and Jacobsohn give the following measurements for a specimen of Lemur 

 macaco {op. cit. p. 174) : — 



Maximum length of cerebral hemisphere 18 mm. 

 Greatest breadth of cerebrum 38 mm. 

 Greatest height of hemisphere 28 in.n. 



» " Oil the liriiin in the Lcnuiis," I'ruc. Zool. Soc. 1895, p. 143. 

 SECOND SERIKS. — ZOOLOGY, VOL. VII I. 50 



