6 H. W. MARETT TIMS. 
naked, darkly pigmented skin area, such as Mr. Beddard has figured and described 
(3) as present, and of systematic importance, in the Otariide. 
Perhaps one of the most interesting points in the external features is what I 
think must be regarded as a vestige of an external ear. In a very early embryo, 
situated just behind the eye is a somewhat circular depression (PI. L., figs. 2 and 3), the 
upper and posterior margin of which is sharply defined. Arising from the bottom of 
this depression, rather towards the posterior part, is a minute, filiform, forwardly 
directed, elevation with a small dark speck at its apex. Whether it is an aperture 
or not I cannot say, but I was unable to insert a bristle into it. This structure was 
bi-lateral, though more distinct on the right side. 
It corresponds so closely to the description given by Howes (4) of the vestiges 
of the external ear in two of the Cetacea that I cannot refrain from quoting his words. 
In a foetal porpoise 22 inches in length was found the external auditory aperture an 
inch and a quarter behind the eye, into which a fine bristle could be passed. “ Over- 
hanging this aperture was a filamentous process of the integument which measured a 
quarter of an inch in length, its pointed extremity being turned forwards, while behind 
it became somewhat broadened, fading off into that covering the head.” 
Still more similar is the description given of the external ear in a foetal Beluga, 
13 inches in length. Howes says (p. 468) that “The external ear opens, in this 
creature, a little above and three-quarters of an inch behind the eye by a minute 
slit-like aperture, somewhat crescentic in shape, and having its concavity turned 
forwards. There projects out of this aperture a delicate filamentous process, having 
the same general appearance as that observed in the porpoise, save that it is more 
slender and appears to spring from the integument forming the posterior lip of the 
aperture rather than altogether behind it.” JI think there can be no doubt that the 
structure present in this foetal seal is the vestige of an external ear, and it is 
interesting to note the close agreement which exists in the last traces of this organ 
in animals of different classes, which have undergone so many similar structural 
alterations in adaptation to their aquatic habit. 
Limbs.—The development of the limbs naturally invites attention on account 
of their adaptive modifications, and it has already been examined to some extent in 
this connection by Professor Leboucq (7). He, however, had a smaller amount of 
material at his disposal, and I think it is possible to add some additional points of 
interest to his published account. The first thing that strikes the observer is the 
precocious development of the hind limb. In fig. 1 the hind limb is as long, if not 
slightly longer, than the fore limb. With the growth of the embryo the total length 
of the latter soon exceeds that of the former, as is seen by a reference to figs. 4, 5, 6. 
This increase is due to an elongation of the femoral and crural segments, since it is not 
until the embryo reaches a body length of about 144 mm. (No. 16) that the length of 
the pes begins to exceed that of the manus, and even then there are individual 
instances in which this is not the case. 
