62 CARL GOTTFRIED HARTMAN 



LITERATURE 



AssHETON, R. 1898 The segmentation of the ovum of the sheep, with observa- 

 tions on the hypothesis of a hypoblastic origin of the trophoblast. 

 Quar. Journ. Alicr. Sci., vol. 41. 



Caldwell, W. H. 1887 The embryology of Monotremata and Marsupalia, 

 Part I, Phil. Trans. Roy. Soc, vol. 178 B. 



Hill, J. P. 1910 The early development of the Marsupalia, with special refer- 

 ence to the native cat (Dasyurus viverrinus). Quar. Journ. Micr. Sci., 

 vol. 56. 



Hill and O'Donoghue 1913 The reproductive cycle in the Marsupial Dasyu- 

 rus viverrinus. Quar. Journ. Micr. Sci., vol. 59. 



MiNOT, Charles R. 1911 Note on the blastodermic vesicle of the opossum. 

 Anat. Rec, vol. 5, no. 6. 



Patterson, J. T. 1913 Polyembryonic development in Tatusia novemcincta. 

 Journ. of Morph., vol. 24. 



Selenka, E. 1887 Studien in der Entwicklungsgeschichte der Theire, Band 

 4, Das Opossum, (Didelphvs virginiana). Wiesbaden. 



PLATE I 



EXPLANATION OF FIGURES 



1 Tubal ovum. No. 76 (3). The distribution of yolk spherules is not quite 

 typical, an unusual numl)er of them having invaded the central, generally yolk- 

 free zone (X 600 j. 



2 Ovarian egg, No. 21 (20), showing discus proligerus (DP), polar bod.v (P5), 

 and chromosomes of the egg nucleus {CH). The zona pellucida is best seen at 

 the lower margin of the egg. The section is taken somewhat to one side of the 

 center (X 430). 



GENERAL ABBREVIATIONS 



CG, coagulum TR.ECT, trophoblastic ectoderm 



CH, chromosomes of egg nucleus Y , yolk 



EMB.A., embryonic area ZP. zona pellucida 



PB, polar body ZR, zona radiata 



»SM, shell membrane 



Note: The figures in these plates were drawn by Miss Aimee Vanneman, 

 technician in the School of Zoology, the University of Texas. The outlines for 

 the drawings were made with the aid of a Bausch and Lomb drawing apparatus. 



