22 JAS. p. HILL. 



EXPLANATION OF PLATES 1 & 2, 



Illustrating Mr, Jas. P. Hill's paper, "^ Contributions to the 

 Embryology of tlie Marsupialia" (II and III). 



All sections drawn were outlined by means of Zeiss's camera lucida. 



List of Common Reference Letters. 



Amti. Amnion, a. v. Branches of vitelline artery on yolk splauclinopleure. 

 all. a. Allantoic artery, all. c. Allantoic cavity, all. cap. Allantoic capil- 

 lary, all. cl. Allantoic canal, all. ent. Allantoic entoderm, all. mes. Al- 

 lanto-cliorionic mesencliyme. all. v. Allantoic vein. Ml. oniph. Bilaminar 

 ompbalopleure. c/i. Chorion, ch, eel. Chorionic ectoderm, cos. Ccelom. 

 c(g. w. Ccelomic wall of allantois. eel. Ectoderm. efiL Entoderm, ex. syn. 

 Syncytium beyond allantoic placental area. mes. Mesoderm of pro-amniotic 

 remnant, pi. a. Allantoic placental area. pi. syn. Syncytium of allantoic 

 placental area. Som. Somatic mesoderm of chorion. Sp. Space in syncytium 

 (lymph space ?). s. t. Sinus terminalis. syn. c. Capillary of syncytium. 

 u. s. Umbilical stalk, ut. w. Uterine wall. vase. omph. Vascular ompbalo- 

 pleure. vil. a. Vitelline artery, vit. v. Vitelline vein. y. spl. Yolk-sac 

 splanchnopleure. 



EiG. 1. — Right uterus, P. obesula, with ventral half of its wall removed 

 and portions of the foetal membranes reflected, to expose the embryo, x 

 nearly J. 



Fig. 2. — The same, after removal of the embryo, to show the placental 

 area (pi. a.). X O^^. 



EiG. 3.— Embryo, P. obesula. x 6/g. 



Ftg. 4. — Transverse section through the umbilical stalk, som. Somato- 

 pleure of body-wall, x 90. 



EiG. 5. — Transverse section through pro-amniotic remnant. X 90, 



EiG. 6. — Section through margin of allantoic placental area. X 120. 



Fig. 7.— Section through allantoic placental area, showing the relation of 

 the foetal and maternal capillaries, x 380. 



Fig. 8. — Section through the sinus terminalis [s. (.), and the adjacent por- 

 tions of the vascular {vase, omph.) and bilaminar ompbalopleure (6il. omph.). 

 X 150. 



Fig. 9. — Uterine embryo of M. par ma in its foetal membranes, seen after 

 removal of the greater portion of the bilaminar omphalopleure. X 7h- 



