490 



ON THE ZOOLOGICAL POSITION 



of this extraorilinary creatui-e, outside Man — perhaps tlie most 

 interesting of all the Monodelphian Mammals. 



I desire to express my thanks to mj Laboratory Assistant, 

 Mr. F. J. Pittoek, for the skill and care lie has expended on the 

 preparation of the Plate. 



Comparative Table, Developmeiit of Prhnates. 



(1) 

 Lemukoids. 



Tarsius. 



1. Development central. ' as in (1). 



2. No attachment to ute-. Attachment very early ef- 

 rine wall. Trophoblastj fucted by localised thick- 

 relatively inactive. i euing of trophohlast. 



3. Amnion formed by fold- 

 formation with proam- 

 nion. 



4. Allantois free and vesi- 

 cular ; unites fairly' early 

 with chorion. 



5. Yolk-sac formed in nor- 

 mal fashion, but is early 

 separated and soon be- 

 comes reduced. 



as in (1), but without pro- 

 amnion. 



(3) 

 Anthropoids. 



as in (1) or interstitial. 



Trophoblastic activity j 

 more marked than in (2).! 

 A single or double at- 

 tachment or interstitialj 

 iinl)eddiiig very early ef- 

 fected. I 



Closed amnion-formation, 

 the primitive amniotic 

 cavity persisting. [ 



Allantois never free and as in (2), but connecting; 

 vesicular, transformed! stalk semivesicular inj 

 into " connecting stalk." Hapale. \ 



Yolk-sac precocious!}' as in (2), but even more 

 formed and reduced from! precocious and more re- 

 the first, never completely! duced. 

 tilling space enclosed by| 

 the trophoblast. | 



6. Formation of extra-em- 

 bryonal mesoderm and 

 coeloni normal, but they 

 extend relatively early 

 through entire omphalo- 

 pleure. 



Extra-embryonal mesoderm as in (2) but distinctly 

 and ccelom precociously! more specialised 

 formed. 



7. Chorion vascularised 

 throughout bj' allantois. 



Chorion extremely thin Chorion vascularised i 

 and non-vascular, except throirghout by way oft 

 overplacental area, which connecting stalk. I 



is vascularised through 

 connecting stalk. 



8. Yolk-sac jilacenta, if 

 present, transitory. 



No yolk-sac placenta. 



as in (2). 



Placenta diffuse, non- Placenta conical, deciduate, Placenta single or douhlej 



deciduate, epithelio-cho- 

 rial in type. 



liiemochorial in type,! 

 but villi not individu- 

 alised and clothed by syn- 

 cytio-trophoblast onl^'. \ 



discoidal and hajmocho 

 rial, villi distinct and 

 projecting into maternal 

 blood-sinus. Troi)lio- 

 blast of villi distinguish- 

 able into syncytio- and 

 cyto-trophoblast. 



