THE EARLY DEVELOPMENT OF THE MARSITPL\LIA. 125 



'05 Van dei- Stricht, O. — "La Striictnre de I'cenf des Mammiferes. 

 Deuxieme partie. Strnctnre de Tceiif ovariqiie de la fenime." " BulL 

 de I'Acad. Roy. de Medicine de Belgique,' Seance du 24 Jiiin, 1905. 



'97 Wilson, J. T., and Hill, J. P. — " Observations upon the Develop- 

 ment and Succession of the Teeth in Perameles ; together with 

 a Contribution to the Discussion of the Homologies of the Teeth 

 in Marsiipial Animals,"' ' Quart. Journ. Micr. Sci.,' vol. xxxix. 



"03 " Primitive Knot and Early Gastrulation Cavity co- 

 existing with independent Primitive Streak in Ornithoi'hynchus," 

 ' Proc. Roy. Soc.,' vol. Ixxi. 



'07 — ■■ Observations on the Development of Ornithorhyn- 



chus," ' Phil. Trans. Roy. Soc.,' Series B, vol cxcix. 



EXPLANATION OF PLATES 1-9, 



Illustrating- Prof. J. P. Hill's paper on " The Early Develop- 

 ment of the Mar.supialia, witli Special Reference to the 

 Native Cat (Dasyurus viverrinus)." 



[All figures are from specimens of Dasyurus. unless otherwise indi- 

 cated. Drawings were executed with the aid of Zeiss's camera lucida, 

 except figs. 61-63, which were drawn from photographs.] 



List of Common Reference Letters. 



Ahii. Abnormal blastomere, fig. 37. alh. Albumen, eg. Coagiilum. 

 (1.2^- Discus proligerus. d. z. Deutoplasmic zone. emh. a. Embryonal 

 area. emh. ect. Embryonal ectoderm, ent. Entoderm. /. ep. Follicular 

 epithelium. /. a. Formative area of blastocyst wall. /. c. Formative 

 cell. /. z. Formative zone. i. c. Internal cell, fig. 34. ?. ent. Limit of 

 extension of entoderm. I. p. Incomplete area of blastocyst wall at lower 

 pole. p. b^. First polar body. 2^- ^'- s. First polar spindle, p. b". s. 

 Second polar spindle. ^>. s. Perivitelline space, .s. m. Shell-membrane. 

 sp. Sperm in albumen, tr. ect. Non-formative or trophoblastic ecto- 

 derm (tropho-ectoderm). y. b. Tolk-ljody. z. ^;. Zona. 



PLATE 1. 



Fig. 1. — Photo-micrograph (x 150 diameters) of the fuU-grown 

 ovarian ovum, -27 X "26 mm. diameter. The central deutoplasmic 

 zone id. z.) and the peripheral formative zone (/. z.), in which the 



