AND AFFINITIES OF TARSIUS. 491 



EXPLANATION OF PLATE L 



Fig. 1. Pliotogi-ai)h (X I'o) of fcetus of Tarsins spectrum (measuring- 2'9 cm. in 

 G. L.), atter removal from the uterine lioni and with the cone-shaped 

 placenta attached. The short uiiiliilical cord is seen to join the chorion 

 shortly after becoming clear of the body of the fuitus and to run down in 

 that mjuibrane to join tlie phicenta marginally. The placenta has l)een 

 divided by a vertical cut, the cut-surface showing {cf. tig. 2 anil explanation 

 thereof). 



[Hubrecht Coll., Tarsius 76. (.'oil. Dr. Fock, Muntolc Bankaleg, I7th 

 Marcli, 1893.] 



Fig. 2. Photomicrograph (X 6) of vertical section of the entire placenta, well to one 

 side of the area of attacliment to the uterine wall. Note the investing 

 chorion with the main stems of the villi arising from it (best seen on upper 

 side of the section), the peripheral Idood-siniises, au<l the large l)!ood- 

 extravasation centrally. 



Fig. 3. Photomicrograph (X 35) of a small portion of the superficial region of the 

 placenta (including the large vjllus \isible in the ujjper left-hand sector of 

 tig. 2). Note the chorion forming the houndarv of the section on tlie 

 upper side, the peripheral blood-sinus, and a large and a small villus-stem 

 arisilig from the chorion, the former showing well the characteristic 

 method of branching. 



Fig. 4. Photomicrograpli (X 80) of a portion of the placenta, situated a little deeper 

 than the base of tig. 3, to show the \illi under higher magnification. The 

 villi are nuiinly (•\it transversely, and in the region photographed are, on the 

 whole, of greater tnan average diameter. Each villus consists of a core 

 of chorionic mesenchyme cari'ying the umbilical \essels and invested hy a 

 more deeply stained sheath composed of a tliin nucleated layer of syncytial 

 trophoblast. An underlying layer of cyto-trophoblast such as is formd in 

 the villi of Anthropoids is at no time present in Tarsius. Adjoining villi 

 are connected by bridges of syncytio-troplioblast, the latter thus forming 

 an irregular network. Between tlic villi are the intervillous spaces, many 

 of them heing more or less completely occujiied by the reticular light- 

 staining material referred to in the text (p. 488). 



Prof. F. Woou-Jt)NES, D.Sc, M.B., F.Z.S. :— Althougli tlie 

 general auatoiuy of Tarsius iumv be said to be fairly well known, 

 there is still great need for complete a,ccounts of dissections of 

 special systems an<l for the general examination of a larger 

 number of speciineus. Apart fi-om the gaps in our knowledge of 

 several important details, there is as yer, no basis for forming an 

 estimate of the range of individual variation. 



As a result of comparing published accounts of the anatomy of 

 Tarsitos and from dissecting an adult female specimen, one can 

 only conclude that either the range of individual variation is 

 considerable or the interpretations of diflei-ent investigatois 

 show a, rather unusual lack of agreement. External characters 

 have been studied in two specimeus, both adult females, and the 

 details of bodily structure in one of them ; in addition, I have 

 had X-ray })hotograplis of various portions of both specimens. 

 [For my material I am indebted to Profs. G. Elliot Smith and 

 J . P. Hill, a,nd for the X ray plates to Dr. Stanley Melville.] 

 For the purpose of this discus.sion it is impossible to furnish more 

 than a summary of the anatomical details, and I have thought it 

 best to mention only the outstanding features which are likely to 

 throw light on the affinities of Tars'ms, dealing especially with 

 those points which link it to, or separate it from, the typical 

 members of the Lemuroidea and Anthropoidea respectively. 



