ON BELMULLET WHALING STATION. 177 
2. Balenoptera sibbaldii (Gray).—The whalebone of this species is 
thicker than that from the ‘J*inner.’ The colour is of a uniform dark 
blue-black colour, both plates and bristles. The average number of 
plates was about 314, and their average greatest length, measured as 
above, was 2 feet 1 inch. ‘ 
X. Hairs. 
1. Balenoptera musculus (L.).—Hairs occur in three positions in 
these animals. At the tip of the mandible and running along the line 
of the symphysis on each side, there were found two rows of short 
hairs, from + to 4 inch in length. The hairs are situated about 1 inch 
apart. ‘The number of hairs in this position is variable, the minimum 
number found being twenty-four (No. 12, Table I.), and the maximum 
forty (No. 30, Table I.). Hairs were also found situated on the dorsal 
side of the head in the beak region. These were arranged in two main 
rows on either side, the inner row on each side curving round the blow- 
holes. The rows were not found to be so regular as those shown by 
Lillie,** however. On each side the rows began about 6 inches from 
the tip of the snout. There were about twelve hairs on each side, or 
twenty-four hairs in all in this position. There was also a row of hairs 
on either side running along the outer side of the lower jaw and parallel 
with the edge. These two rows each consist of from six to ten hairs. 
- When a hair is situated on a dark portion of the skin, there is often 
a light-grey ring round its base, but this ring is not invariably present. 
- When the hair is situated on a pale portion of the skin, e.g., on the tip 
of the mandible, we generally find a dark ring round the base. No 
sebaceous glands connected with these hairs could be found.*® There 
appeared to be a small nerve connected with the papilla of each of these 
hairs,4° so that they -probably have some. sensory function, e.g., the 
detection of food. - 4 
2. Balenoptera sibbaldii (Gray).—The distribution of hairs in this 
species is almost exactly similar to that in the common ‘ Finer.’ The 
number of hairs in the different positions is not quite the same in the 
two species, however. At the tip of the lower jaw there generally 
appeared to be about forty hairs. In No. 5, Table ILI., there were 
forty-four. Along the top of the beak we have about fifteen hairs on 
each side, or thirty in all. The number along the edge of the lower 
jaw is generally six. The hairs are of the same dirty-white colour as 
in Balenoptera musculus, but there is never a light-grey ring round the 
base of any of the hairs. 
XI. Jacopson’s ORGAN. 
This organ *! appears to be represented only by the ventral ends of 
Stenson’s duct on each side, which open underneath the tip of the 
snout. The openings are situated about 3 inches from the tip of the 
88 Lillie, Proc. Zool. Soc., 1910, 2, p. 774. 
39 So also Kiikenthal, ‘Walthiere,’ in Denkschr. Med.-Nat. Gesells., Jena, 
1889. , 
4° Vide Japha, Zool. Jahrb., xxiv. ; 
41 Lillie, Proc. Zool. Soc., 1912, 2, p. 784; Kikenthal, op. cit., p. 349, vol. ii. 
1912. N. 
