LIDS POSTCAVAL VEIN IN MAMMALS. 52) 
Georychus, and some other “genera agree closely, while Zapus and 
Gerbillus seem to approximate to the tee I Opinions as to 
the classification of Rodents vary greatly *. 
§ Some Variations of the Postcaval Trunk. 
Under this heading should no doubt strictly be included a very 
large proportion of the facts with which I deal in the present 
communication. I limit myself, however, in this section to two 
cases of apparently abnormal position of the postcava; “abnormal” 
because they are not like any condition of that vein which is 
characteristic of a given group or even minor subdivision of any 
mammalian order. From this point of view, therefore, I cannot 
include the occasional duplication of the postcaval in Hrinaceus, 
since it would appear to be fairly common in that genus, and is 
also a marked character of the Edentata, &c. Moreover, it might 
be urged that the single postcaval lying to the right of ‘the aorta 
is the abnormal condition i in Hrinaceus ewr opus. 
In an example of Chiromys madagascariensis dissected in 
September of last year I found that postrenally the posteaval 
vein lay to the left instead of to the right of the aorta. The 
normal condition of this vein has been already and quite recently 
described by myself 7. “The arrangement of the spermatic or 
ovarian veins as the case may be appeared to me to differ in the 
two sexes, and did undoubtedly differ in the two individuals upon 
which I reported to the Society. Im both individuals the right 
spermatic or ovarian vein flowed into the postcava rather distally 
but still some way in front of the posterior bifurcation of that 
vein. In the female the left ovarian flowed into the left renal, 
while in the male the corresponding spermatic vein flowed into 
the postcaval a little way anterior to the entrance of the right 
spermatic vein. The relative position of these veins in the 
male is important to be borne in mind. In the abnormal 
example of Chiromys to which I refer in the present communi- 
cation, the relative position of the two spermatic veins was—in 
correspondence, as I imagine, with the sinistral posteava— 
entirely reversed. The right spermatic vein entered the postcava 
anteriorly to the left. 
There was, however, no reversion in the position of the renal 
veins ; they lay exactly as in the two normal examples described 
by myself. It may be worth while mentioning that in this 
abnormally veined Chiromys the small anterior lumbar parietal 
vein, to which I directed attention as occupying in the male the 
position of the ovarian vein in the female, is present; it lies, 
however, on the opposite side of the renal and therefore ends 
anteriorly ; it is not to be confused with a suprarenal vein. This 
variation in Chiromys madagascariensis seems to be exactly 
paralleled in a variation of Homo sapiens referred to by 
* Of. e.g, Thomas, P. Z.S. 1896, and Tullberg, Nov. Act. Upsala, 1899. 
+ P.Z.S. 1908, p. 700. 
Proc. Zoot. Soc.—1909, No. XXXIV. 
(Su) 
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