THE EVOLUTION OF A BURSA 185 



On hand and foot first phalangeal joints, bursas present, 

 on second row absent. 

 C and D were similar. 



Metacarpo- and metatarso-phalangeal joints, none in C 



and scanty in D. 

 No bursse on any phalangeal joints of hand or foot. 

 Orangs. 



E. Metacarpo- and metatarso-phalangeal joints, bursas ill- 



developed, first row of phalangeal joints of hand and foot 

 moderate, second row none. 



F. Metacarpo- and metatarso-phalangeal joints more marked 



than in E., and well developed on all phalangeal joints. 

 Gibbons. 



G. Metacarpo- phalangeal and metatarso-phalangeal joints 



poorly developed on D 2, 3, 4, 5, and none on those of D 1. 

 Absent on all phalangeal joints. 



The digits of the gibbons were very long and evidently 

 efficient in action, but were never flexed to any great degree. 



Dead Specimens. 



I also examined the hands and feet after death of certain lower 

 Primates in 1909 : — 



H. Hapalemur Griseus. 



I. Hapale Jacchus. 



J. Cercopithecus Callitrichus. 



K. Cercopithecus Mona. 



L. Macacus Rhoesus. 



Hapalemur Griseas H. Hands. No bursas on styloid processes of 

 radius and ulna, and no localised bursas on any metacarpo- 

 phalangeal or phalangeal joints. 



Feet. Bursas under tendo achillis small but distinct. Present 

 over both malleoli. 

 Metatarso-phalangeal joints D 1, 2, 3, rudimentary 



D 4 and 5 absent. 

 Fiist phalangeal joints of D 1, 2, 3, 4, rudimentary 



absent over D 5. 

 Second phalangeal joints absent on all digits. 



Hapale Jacchus I. 



Hand. Lower end of ulna, which is very prominent, a bursa 

 present, over end of radius, which is much less 

 prominent, absent. 

 Metacarpophalangeal joints, present in all. 



