30 CARL G. HARTMAN 
the egg of Dasyurus, which measures 0.21 x 0.126 to 0.27 x 0.26 
mm. The ova shown in figure 1, plate 13, and in figure 1, 
plate 14, are unusually large, even for ovarian eggs, measuring 
0.183 x 0.156 mm. (average 0.175 mm.) and 0.185 x 0.15 (average 
0.167) mm., respectively. That the ovarian ova are on the 
average larger than the tubal or the uterine ova would seem to 
be the case from the few measurements of ovarian eggs that 
have been made. There is, of course, considerable variation in 
the sizes of different eggs, both of the same litter and of different 
litters (fig. 2, pl. 3, figs. 2 to 6, pl. 13). 
The ova are surrounded by a well-defined zona pellucida, 
within which the polar body is found. This is given off usually 
at one of the ends of the somewhat elongated egg (fig. 1, pl. 13), 
but it may be found near the equator. The polar body is small 
and flattened, and contains chromatin matter and a minimum of 
cytoplasm. The chromosomes of the egg nucleus lie in the 
cytoplasm near the polar body, mostly more or less discrete 
and arranged in an equatorial plate. In this condition the egg 
reaches and traverses the Fallopian tube. 
The ovarian egg is, therefore, essentially like the tubal ovum 
presently to be described in greater detail. There is no polar 
differentiation recognizable except for the location of the polar 
body. It is important to note also that the yolk has no tendency 
to accumulate at one pole of the egg, as is so strikingly the case 
in the mature ovum of Dasyurus and to a slight degree in 
certain Eutherian eggs (bat, armadillo). Herein lies the first 
striking difference between the eggs of Didelphys and the 
Australian Dasyurus. 
b. The tubal ovum 
1. Material, ovulation, secretion of albumen and shell membrane. 
Eggs were removed from the Fallopian tubes of five animals, 
but in no case was insemination observed. Unfortunately, 
none of the thirty or more eggs sectioned contains any trace of 
a spermatozoon. This stage has, therefore, not yet been 
observed in the case of any marsupial. 
