453 



also be mentioned at this point that when the V. cava posterior 

 was bifurcated as far forward as the Vv. spermaticae, in every 

 instance, either one or both of the Aa. spermaticae passed ventrad 

 between the bifurcated divisions near their point of union. See 

 Figs. 3 and 4. 



The probable significance of the above mentioned variations 

 in connection with the formation of the V. cava posterior. 

 All variations in connection with the V. cava posterior must, 

 naturally, as Hochstetter^) says, fall under two great groups: 



"Die eine Gruppe von Varietäten umfaßt Fälle, in denen das 

 Venensystem in den uns interessirenden Abschnitten auf irgend einer 

 jener Entwickelungsstufen, welche es sonst unter normalen Verhält- 

 nissen zu durchlaufen pflegt, stehen geblieben ist und sich an dem- 

 selben nichts weiter geändert hat, als was sich wegen der im 



developed A a. ovaricae, both of which had exactly the 

 same distribution, namely, to the ovaries and proximal 

 portion of the uterus. 



The posterior pair are those which have been described in the 

 preceding pages under the name of the Aa. spermaticae internae 

 {A.s.i. in Figs.). These arteries arise from the Aorta about opposite 

 the interspace between the fifth and sixth lumbar vertebrae and cor- 

 respond, in their point of origin from the Aorta, to the usual origin of 

 the A. mesenterica inferior of most mammals. (See Hochstetter's 

 Fig. 25, Taf. XXIII, Morph. Jahrb., Bd. 20, for origin of A. mesenterica 

 inferior and compare with my Figs. 3 and 4.) 



This last mentioned artery in Didelphys Virginian a, however, 

 usually arises from the Aorta in common with the A. mesenterica 

 superior and A. coeliaca. This common trunk (Truncus coeliaco-mes- 

 entericus) arises from the Aorta about opposite the interspace between 

 the first and second lumbar vertebrae. 



The anterior pair of A a. ovaricae, were given off 

 from the Aorta, as single vessels, about opposite the 

 middle of the third lumbar vertebra and ran, on each 

 side, directly to the ovaries where they anastomosed 

 with the so-called posterior ovarian arteries (A.s.i.). 



Whether these anterior ovarian arteries were present in every 

 individual examined, I am unable to say. It seems probable, however, 

 that they were, and that on account of their small calibre in animals 

 outside of the breeding season, the arteries were not filled with the 

 gelatine injection mass and were thus overlooked. The posterior 

 ovarian arteries (A.s.i.), however, were always injected and undoubt- 

 edly correspond, at least functionally, with the so-called Aa. spermaticae 

 of mammals. 



1) Morph. Jahrb., Bd. 20, p. 629. 



