FCETAL MEMBRANES OF CHIROMYS MADAGASCAKIENSIS. 1165 



and the latter " plicate." Both are plicate in Assheton s sense, 

 and are characterised on the fostal side by the presence of a 

 relatively passive trophoblast, markedly folded and of great 

 extent, by the vascularisation of the chorion through a large 

 vesicular allantois and by the reduction of the yolk-sac and its 

 vessels ; and on the maternal side, by the persistence of the 

 uterine epithelium (at least in the majority) and of the uterine 

 glands in an active functional condition. In our view, the 

 resemblances far outweigh the differences in detail. 



We are accordingly in entire agreement with Jenkinson (16) 

 in believing (1) that the resemblance between the non-deciduate 

 placentation of the Lemuroids and that of other Mammals, e. g. 

 the Ungulata, are due to their derivation " from a common 

 ancestral ' indeciduate ' type"; and (2) that the deciduate 

 hfemochorial type of placenta characteristic of the other Pri- 

 mates has been evolved from the non-deciduate Lemuroid tj^pe, 

 qiiite independently of that of the "Rodents. Insectivora, etc. — 

 another illustration of the principle enunciated by H. F. Osborn 

 that " the same results appear independently in descendants of 

 the same ancestors." 



^' e are greatly indebted to Mr. F. Pittock for invaluable help 

 in the preparation of Pis. III.-VI. and to Mr. S. Steward for the 

 photographs of Specimen A, Pis. I. k II., and to Mr. Terzi for 

 retouching the same. 



APPENDIX. 



On the External Characters of a Foetal Chiromys. 

 By R. I. PococK, F.R.S. 



At the request of the authors, I undertook to examine and 

 describe the external features of the foetal Chiromys (Specimen B, 

 PL III. fig. 6), the placenta of which is described in the pre- 

 ceding pages hj Prof. Hill and Mr. Burne. 



The approximate dimensions in millimetres of the specimen, a 

 male apparently at full time, are as follows : — Dorsal contour 

 length (snout to root of tail) 165 ; head and body from croAvn to 

 root of tail 106 : head from nose to occiput 37 ; ear from inter- 

 tragal notch 21 ; tail 103 ; upper arm 25 ; fore-arm 21 ; palm of 

 hand 12 ; thigh 31 ; lower leg 31 ; sole of foot 18. The general 

 proportions do not difier greatly from those of the adult, the tail 

 and arm being relatively as long, but the head is relatively 

 larger, the leg shorter, and the digits of the hand shorter than 

 in the adult. 



The coat consists of comparatively short and sparse adpressed 

 hairs, brown and grey in colour ; on the hands and feet and tail 



