v.e.) run
to the internal border of the anterior part of the kidney, which answers,
therefore, to the rabbit's epididymis. The hinder part of the kidney is
the predominant renal organ. There is a common uro-genital duct, into
which a seminal vesicle, which is especially large in early spring,
opens. This is the permanent condition of the frog. In the rabbit, for
urogenital duct, we have ureter and vas deferens; the testes and that
anterior part of the primitive kidney, the epididymis, shift back into the
scrotal sacs, and the ureters shift round the rectum and establish a
direct connection with the bladder, carrying the genital ducts looped
over them. The oviducts of the female do not fuse distally to form a
median vagina as they do in the rabbit. In front of the genital organ in
both sexes is a corpus adiposum (c.ad.), which acts as a fat store,
and is peculiar to the frogs and toads. The distal end of the oviduct of
the female is in the breeding season (early March) enormously
distended with ova, and the ovaries become then the mere vestiges of
their former selves. The distal end of the oviduct is, therefore, not
unfrequently styled the uterus. There is no penis in the male,
fertilisation of the ova occurring as they are squeezed out of the
female by the embracing fore limbs of the male. The male has a pad,
black in winter, shown in Figure 1, which is closely pressed against
the ventral surface of the female in copulation, and which serves as a
ready means of distinguishing the sex.

Section 17. The spinal cord has a general similarity to that of the
rabbit; the ratio of its size to that of the brain is larger, and the
nerves number ten pairs altogether. The first of these (sp. 1, in
Figure 2, Sheet -12- ) {First Edition error.} [13] corresponds in
distribution with the rabbit's hypoglossal nerve, a point we shall refer to
again when we speak of the skull. The second and third constitute the
brachial plexus. The last three form the sciatic plexus going to the
hind limb.

Section 18. The same essential parts are to be found in the brain of
both frog and rabbit, but in the former the adult is not so widely
modified from the primitive condition as in the latter. The fore-brain
consists of a thalamencephalon (th.c. and 1), which is exposed in the
dorsal view of the brain, and which has no middle commissure. The
cerebral hemispheres (c.h.) are not convoluted, do not extend back to
cover parts behind them, as they do