A CONTRIBUTION TO THE ANATOMY AND DEVELOPMENT 
OF THE VENOUS SYSTEM OF DIDELPHYS MARSUPI- 
ALIS (L).\—PART I, ANATOMY. 
BY 
CHARLES F. W. McCLURE. 
Professor of Oomparative Anatomy, Princeton University. 
Witu 5 CoLORED PLATES AND 11 TEXT FIGURES. 
It has been found necessary to publish this paper in two parts. The 
first part deals with the anatomy of the venous system of Didelphys 
marsupwalis, while the second part, which appears later, will deal with 
the development of the veins. 
In 1900 the writer’ published a preliminary article entitled “The 
Variations of the Venous System in Didelphys virginiana,” in which 
was described a set of variations that occurred in connection with the 
mode of origin of the postcaval vein. These variations were so unusual 
in character and occurred with such regularity in all of the opossums 
examined that a further investigation was deemed necessary. This 
investigation is now completed and after the examination of one hun- 
dred and one (101) opossums the writer can reiterate the statement 
made in the preliminary article, that the mode of origin of the post- 
cava is so variable in Didelphys marsupialis, that it is impossible to 
assign any one mode of origin for this vessel that may be regarded as 
typical of the species. ) 
It is astonishing how little has been published upon the anatomy of 
the venous system of marsupials when one considers the unique char- 
acter of their postcaval vein. Previous to 1893 the writer has, with 
Hochstetter, 93, been able to find in the literature but one reference to 
the postcaval vein (Owen, 66), in which it has been described as occu- 
10n the basis of priority of nomenclature the specific name marsupialis has been 
substituted for virginiana. All of the opossums made use of were captured in the 
neighborhood of Princeton, New Jersey. 
2The writer wishes to express his thanks to Stephen 8S. Palmer of New York, for 
his generosity in supplying the funds necessary to cover the cost of the Plates in this 
article. Also to his assistant C. F. Silvester thanks are due for his valuable assist- 
ance in connection with the preparation of the material used in the investigation. 
