6 II. W. MAHKTT TIMS. 



naked, darkly pigmoiited skin area, sueh as Mr. Beddard has figured aud descriVjed 

 (3) as present, and of systematic importance, in the Otariidse. 



I'crhaps one of the most interesting points in the external features is what I 

 think must l)e regarded as a vestige of an e.xternal ear. In a very early embryo, 

 situated just liehind the eye is a somewhat circular depres.sion (I'l. I., figs. 2 and 3), the 

 up|)er aud po.storior 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, hut I was unable to insert a bristle into it. This structure was 

 bi-latcml, though more distinct on the right side. 



It corresponds so closely to the description given by ILjwes (4) of the vestiges 

 of the external ear in two of the Cetacea that I cannot refrain from quoting his words. 

 In a fivtal 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 jwssed. " Over- 

 hanging this aperture was a filamentous process of the integument wliich 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 ujore similar is the description given of the external ear in a foetal Beluga, 

 13 inches in length. Ilowes 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 sjime general appearance as that observed in the porpoise, save that it is more 

 slender and appears to spring from tlie integument forming the posterior lip of the 

 aperture rather than altogether behind it." I think there can be no doubt that the 

 structure present in this fa'tal 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 diHerent classes, which have undergone so many similar structural 

 alterations in a<laptation to their aquatic liabit. • 



Limhs. — The development of the limljs naturally invites attention on account 

 of their adaptive modifications, and it has already been examined to some extent in 

 this connection by I'rofes.sor Lcbouccj (7). He, however, had a smaller amount of 

 material at his dispo.sal, and I think it is po.s.siblo to add some additiimal points of 

 interest to his published account. The first tiling that .strikes the ob.server is the 

 ]»rccocious development of the hind lind). 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. 10) that the length of 

 the pes begins to exceed that of the manus, and even then there arc individual 

 instances in which this is not the ca.se. 



