1864.] IN THR MUSEUMS OF HOLLAND AND BELGIUM. 385 
foetal life in cartilage ; and the peculiar characteristics of the mature 
animal can be obtained far more accurately from the examination of 
such a specimen, than from that of the bony portion only of the par- 
tially ossified skeleton of a half-grown individual. 
In young skeletons all the bodies of the vertebre have readily 
detached disk-like epiphyses at each end. These commence to unite 
to the main portion of the bone at the two extremities of the series, 
the union in the case of the central vertebre not taking place until 
most other signs of immaturity in the skeleton have disappeared. I 
have observed also that in the individual vertebre it is usually the 
epiphysis furthest removed from the middle of the column, 7. e. the 
auterior one in the cervical region and the posterior one in the caudal 
region, which first join the body of the bone. It is stated by Pro- 
fessor Owen that “ this embryonic condition is not obliterated at any 
age in these gigantic aquatic mammals, which, being sustained in a 
medium of nearly their own specific gravity, have more need of 
flexibility than firmness in the vertebral column’’*. Certainly in 
the large majority of museum specimens the vertebral epiphyses, at 
least in the dorsal and lumbar regions, are still unattached ; but their 
union with the bodies of the vertebrae, and the complete obliteration 
of all trace of their original autogeny, throughout the vertebral column 
in the adult animal is well seen in the large skeletons of Common 
Fin-Whales (PAysalus antiquorum) in the British Museum, Alex- 
andra Park, Rosherville Gardens, and Antwerp Zoological Gardens. 
The humerus has two epiphyses, upper and lower; the radius and 
ulna also two each. The order in which these unite to the diaphysis 
is as follows :—That of the lower end of the humerus and upper end 
of the ulna and radius about the same time, then that of the upper 
end of the humerus; these are all united before the epiphyses of the 
bodies of the dorsal and lumbar vertebree. Lastly, and only at a 
comparatively late period of life, when the vertebral column is com- 
pleted, do the peculiar small rough nodules of bone developed in the 
mass of cartilage which forms the lower end of the radius and ulna 
become united to the shaft. 
The obliteration of the sutures of the cranium affords some indi- 
cations as to age: for instance, the distinctness of the basisphenoid 
from the presphenoid and basioccipital bones, and of the exoccipitals 
from the supraoccipital, indicates a very early condition; but after 
the union of these, very little change takes place, except the soldering 
of the supraoccipitals with the parietals and frontals, the majority of 
the bones remaining, as far as I have yet had an opportunity of 
observing, distinct and separable throughout life. 
Weare able from these indications to divide, for practical purposes, 
all the skeletons that may be met with into three stages of growth. 
I. In the first, all the epiphyses of the vertebral column, and of both 
ends of the humerus, radius, and ulna, are still separate, and the 
processes of the vertebree are very incomplete. The animal remains 
in this condition uutil it has attained to more than half the length of 
* Descrip. Cat. Osteol. Series, Mus. Roy. Coll. Surgeons, 1853, vol. ii. p. 440. 
Proc. Zoou. Soc.—1864, No. XXV. 
