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Show 1S89.] ANATOMY OF THE KANGAROO. 437 The allantois was represented by a shrivelled cord-like structure terminating in a blunt club-like extremity, lying alongside the other constituents of the cord and easily separable from them. This allantois was continuous with the fundus of the bladder, from which it extended 8 mm. Along with the question of the route outwards of the embryo has been discussed also the route inwards of the seminal fluid, whether, in fact, this goes by the lateral canal or by the median canal when this is open. I am able to throw some light on this point (at least for Macropus major) by the receipt recently of a specimen of the female organs of an adult of this species shot immediately after an observed act of coitus. In this specimen, which is represented in the drawing (fig. 2, p. 438) about one half of the natural size, the lateral canals were enormously distended by what proved to be six and a quarter ounces (by weight) of a viscid tenacious mucus-like substance containing abundant spermatozoa. The median canal was also distended to a size which would, in its upper part, more than contain two good-sized thumbs, and which contained some of the same kind of mucus-like material as that in the central canals, the mass in each being continuous. In its lower third the median canal narrowed down to a size that would scarcely admit a pencil. The opening between the median and each lateral canal was very large and patent, admitting a large thumb easily. Both anterior (ventral) and posterior (dorsal) walls of the median canal were no thicker than stout parchment, and the internal surface of the former showed a distinct median raphe, which, as in the preceding specimen, rose into such a well-marked ridge in the lower part as to divide the passage into two similar well-marked channels. The same striated and reticulated appearance of its walls in the lower part also existed. Between the median canal and the urogenital passage there was a well-defined but small passage that would barely admit an ordinary steel knitting-needle. Seven m m . below this aperture, on the anterior (ventral) wall of the urogenital passage, was the orifice of the uretha (u, figs. 2 & 3); and between these two openings extended a laterally compressed keel-like projection (vide figs. 2 &, 3,f), 5 m m. in height, thin at its free edge, springing from a base (6 m m . long and 3 mm. wide) from the posterior (dorsal) surface of the urethra. In fact the urethra might be described as piercing longitudinally the base of this projection. Both the urethral orifices and this keel-like ridge occupied a narrow ellipsoidal and depressed area marked off by a well-marked (g, fig. 3) ridge of corresponding outline. Situated in the middle line, exactly midway between the orifice of the urethra and the joint outlet of the combined urogenital and rectal canals, was a flat tongue-like process (Y, fig. 2), compressed dorso-ventrally and pointing inferiorly towards the outlet of the passage. This covered up a cul-de-sac, which extended upwards under it for 5-6 mm., and with a similar width. Ou the posterior dorsal surface of this tongue-like flap was anoiher smaller cul-de-sac, leading upwards also for about 3 mm., and with about the same |
