1864.] iN THE MUSEUMS OF HOLLAND AND BELGIUM. 387 
least probable that the same laws govern the different members of a 
group so well-defined as the Whales. No species of Balzenoid Ce- 
tacean is so well determined as the Northern Right Whale (Balena 
mysticetus), and of none are we able to adduce so many instances 
of the size that various individuals of the species have attained. 
A skeleton in a late stage of the adolescent period in the Museum 
at Brussels measures a little over 50! in length; and Scoresby, as is 
well known, states that out of 322 examples examined by him no 
one exceeded 60! in length; indeed the largest measured was 58’, 
being one of the longest, to appearance, that he ever saw. The 
adult animals must then have a tolerably limited range of varia- 
tion, within a few feet of either side of 55'. Again, the common 
and well-marked species Balenoptera rostrata, the dwarf of the 
family, is still in the adolescent stage at 25! long, and there is 
no instance recorded in which it exceeded 31'. The adult Hump- 
backed Whale (Megaptera longimana) appears to range within 45! 
and 50! in length. In the Common Fin-Whale (PAiysalus anti- 
quorum) we have evidence of variation at an adult age and in the 
same, (male) sex, of from 60! (Rosherville Gardens) to nearly 70! 
(Alexandra Park and Antwerp Zoological Gardens). It is possible 
that this species may sometimes attain a few feet longer, but all the 
cases in which this is stated require fresh investigation. The alleged 
length of a Whale in the flesh is rarely to be depended on, and even 
the given measurements of skeletons are often inaccurate, as much 
depends upon the method of articulation. Size being in the popular 
mind a point of vital importance in a Whale, the tendency to exagge- 
rate this quality is a constant obstacle to exact investigation. We 
may conclude, then, that all the evidence at present available tends 
to prove that the idea which some naturalists entertain, that Whales 
have no definite limit to their growth, is incorrect, and that, as in 
other mammals, there is an average size to which each species attains, 
subject to individual differences within a moderate range. 
The number of vertebree and number of ribs have been supposed 
to be subject to considerable individual variation, partly in conse- 
quence of several distinct species having been confounded, and partly 
from the loose way in which these bones have been counted from 
defective or badly articulated skeletons; but in fact, subject to the 
exceptional circumstances about to be mentioned, they are quite as 
constant among the Cetacea as among other Mammalia, and are 
therefore characters of the highest importance in determining species. 
Every example of Balenoptera rostrata that | have examined in 
museums, or found recorded, has eleven pairs of ribs, and a total 
number of vertebree amounting to 48 or 50. In like manner skele- 
tons of Physalus antiquorum, when complete, appear always to have 
15 pairs of ribs and 61 or 62 vertebree. Megaptera longimana has 
14 pairs of ribs and 53 vertebrze; Balena mysticetus 12-13 pairs 
of ribs and 54 vertebrae. It frequently happens that the last pair of 
tibs only attain a rudimentary condition, and, their heads not arti- 
culating with the vertebrze, they are lost in preparing the skeleton. 
This condition of the last (15th) pair of ribs is well seen in the ske- 
