ON BELMULLET WHALING STATION. 179 
The pupil is elongated antero-posteriorly and has a peculiar shape. 
When expanded the pupil is nearly in the shape of a half-ellipse, the 
curved side being ventral. On contraction the curved part remains 
practically stationary, and the upper, originally nearly flat, boun- 
dary is allowed to drop downward. When closed the pupil is prac- 
tically in the form of a semicircular line with the convexity downwards. 
This peculiar shape of pupil is found also in the bottlenose porpoise.‘? 
The internal structure of the eye, as far as could be ascertained 
from the specimens examined, conformed to the normal mammalian 
type, with certain modifications which are usually considered to be 
adaptations to an aquatic mode of life. These consist chiefly in the 
presence of a thick sclerotic, a flattened and fairly thick cornea, and a 
nearly globular lens. All these modifications are well marked in the 
eyes of B. musculus and B. sibbaldii. 
The chief points of anatomical detail noticed were :— 
(a) No Meibomian glands could be found in connection with the 
eyelids. 
(b) The musculature of the iris is well developed. 
(ec) The choroid is thin, and the ciliary muscle appears to be 
entirely absent. 
(d) There are four large venz vorticose in the sclerotic. 
(ec) There are many rods and cones in the retina, of medium 
length. The most noticeable thing about the retina is the 
large number of elements composing the outer nuclear 
layer, which is much thicker than the inner. 
XIV. PARAsItTEs. 
A. External. 
1. B. musculus (Lu.).—In about half a dozen cases the parasitic 
copepod Penella balenoptera (Koy. and Dan) was found on the body of 
this species. The external portion of the body of these parasites aver- 
aged about 6 inches in length. The parasite was of a black colour, 
except the egg-sacs of the female, which were in the form of long, 
narrow brown strings, less than a millimetre broad and about as long 
as the projecting part of the body of the parasite. 
These parasites are generally found all through the season, and the 
most usual position is on the body-wall not far behind the ear-opening. 
In some cases they were found on the side of the whale, near the tail. 
The greatest number found on one whale was six. 
The other external parasite found on this species is the copepod 
Balenophilus unisetus (Aurivillius). These occur on the baleen-plates. 
Both nauplius larve and adults are found on the plates, and when large 
numbers of nauplii are present they are situated chiefly on the outer sides 
of the plates. When few of these parasites are present they are gene- 
rally on the inner sides of the plates. This parasite was not present on 
eyery specimen of B. musculus examined. 
2. B. sibbaldii (Gray).—The small copepod Balenophilus wnisetus 
“ True, Proc. U.S. Nat. Mus,, vol. xiii., p. 197. 
N 2 
