524 MR. F. E. BEDDARD ON THE [Apr. 27, 
system that it is rather premature at present to attempt to lay 
down any statement of general application. But such facts as 
we have distinctly prove that the Insectivora occupy a somewhat 
midway position. They are at least commencing to lose the 
double postrenal caval. Still it is very frequent. Whether 
Hochstetter’s discovery of a similarly divided postcaval in 
Pteropus * will prove this condition to be characteristic of the 
Bats—or at least the Fruit-Bats—remains to be seen, as also 
whether the Cetacea are largely or mostly thus to be charac- 
terised. It can be safely said that the Carnivora yt only show 
remnants of this state of affairs; but such rudiments are not 
without significance inasmuch as they occur among the Arctoidea, 
which are perhaps to be regarded as the most primitive among 
the Carnivora. McClure’s interesting discovery, confirmed by 
myself, of the condition of the postcaval in the Ungulate 7’ragulus 
adds one Ungulate genus to this same category ; but as this group 
has been but little studied from the present point of view, it 
would be premature to base any arguments upon the facts. In 
contradistinction to the groups of mammals already considered, we 
have the Rodentia, Lemuroidea, and Primates, which invariably 
show a postcaval vein lying to the right of the aorta postrenally 
and possessing no fellow upon the opposite side. That variations 
have been described does not alter the fact that these Kutherian 
mammals differ from the Eutherian groups already dealt with. 
It is true that here again the actual facts known require much 
increase before any generalisations can certainly be made. But 
the evidence is already sufficient to be seriously considered. It 
will be noted that those orders of mammals which show a 
retention of the Monotreme condition are admittedly primitive ; 
and it may be further said generally that the greater or less 
persistence of this condition is in relation to their position in 
the series. Thus the Marsupials, Edentates, and Insectivora are, 
in the opinion of all zoologists, ancient groups. On the other 
hand, the Ungulates and Carnivora are more advanced in many 
ways, while the Primates are still more specialized in some 
respects. It is also noteworthy that of those types among the 
more modern and specialized groups which show the character 
under discussion, it is clear that they are more primitive types 
than are some of their allies. The Chevrotains stand below the 
Deer and Antelopes, and the Arctoid Carnivores? are nearer to 
the common stem than are the Cats. 
The differences observable among the genital veins are not a 
* Tbid. p. 619 and references there quoted. 
+ Beddard, P. Z.S. 1909, p. 491, text-fig. 13. 
+ I take this opportunity of stating that in an example of Mellivora signata (in 
fact, the type specimen described by Pocock, swpra, p. 394) the postcaval was divided. 
The division ran up to just behind the entry of the left renal vein, as in an example 
of Ictonya recently described by myself (supra, p. 491). The right renal vein entered 
higher up. The ovarian veins were symmetrical and entered the divided postcaval ; 
below them entered the also symmetrical lumbar parietal veins. No ovarian branches 
entered either renal vein. I have figured these veins in the memoir referred to 
(v. supra, p. 491, text-fig. 131 A). 
