by Frank E. Beddard. 145 
the older fcetus upon the same plate and with my earlier illustration 
of a still older foetus, that the tail is more distinctly marked off from 
the body in the very young fcetus, thus emphasising the mammalian 
character, and not nearly so well marked in the older feetus, whence 
The 
second matter concerns an anal fin, the existence of which Kiikenthal 
they agree with the adult in possessing a fish-like symmetry. 
asserts and figures in the genus Megaptera*, quoting other authorities. 
Whether the ventral ridge which I have referred to above in the 
youngest foetus of the Cachalot is to be placed in this category or not 
I do not know. It might also be held that the “continuation ” of the 
dorsal fin which I have also referred to in that small foetus presents 
evidence of a former more extensive dorsal fin. | And in considering 
this possibility it must be borne in mind that in Delphinapterus, where 
the dorsal fin is absent in the adult whale, there is a distinct ridge in 
the festus which later in development disappears. 
GENITAL REGION. 
The fcetus described in my earlier paper is a female; the two dealt 
within the present communication are both males. In the larger of 
these latter the penis (see text-fig. 12) is directed backwards and lies 
with in the ventral gutter which terminates posteriorly with the anus. 
This is most suggestive of a cloaca. The length of the cloacal gutter 
is 6 mm. and the penis is a trifle shorter, not quite occupying the whole 
of the space available. The two mammary grooves are plainly visible, 
lying quite parallel to the gutter, rather nearer to the anterior end of 
the same, but extending back to the middle. These grooves measure, 
each of them, 2 mm. ‘They are thus one-third of the length of the 
cloacal groove. In the youngest feetus the arrangement of these various 
parts (see text-fig. 8) was different owing to the eversion of the gutter 
which was thus apparently a part of the penis, which latter is directed 
forwards and not backwards as in the older feetus. I could find here 
no mammary grooves; the distension of the genital region has perhaps 
temporarily obliterated them. In the larger female foetus formerly 
described by me the cloacal or vulvo-anal groove was 18 mm. in length; 
and it is noteworthy that the mammary grooves—in spite of the fact 
that the animal is a female—are 6 mm. in length and thus no longer 
proportionately than in the younger male animal. In both cases the 
* Jen. Zeitshr, Bd. LI. 
