ON BELMULLET WHALING STATION. 155 
characteristic of the Cetacea. The duration and manner of effecting 
this are.very definite, according to the whalers, and are different for 
different kinds of whales. Thus it is said that the common ‘ Finners’ 
(Balenoptera musculus, L.) continually ascend and descend with an 
almost undulatory motion. Blue whales (Balenoplera sibbaldii, Gray), 
on the other hand, behave somewhat differently. They appear at the 
surface, give a definite number of blows or spouts, and then dive, 
apparently fairly deeply. They then remain submerged for a definite 
time. The time of submergence and the number of expirations on 
rising to the surface appear to be directly proportional to one another. 
Thus, if a submergence of 10 minutes is followed by six expirations, a 
dive of 5 minutes’ duration will be followed by three ‘ blows.’ It is 
said that the phenomenon may be accurately timed by a watch. 
Of course the great regularity is only found when the whales are 
progressing normally and are not being chased. With regard to the 
possible duration of submergence, the whalers believe that whales can 
remam under water for a comparatively long period if they wish. 
Sometimes, when plenty of whales can be seen at one place, they 
will disappear for perhaps twelve hours, and then all appear again. 
Where do they go? It is certainly very questionable whether they can 
possibly be submerged all the time. The ‘ reappearance’ may merely 
show the presence of another ‘ school’ altogether, though the whalers 
do not seem at all certain about this. 
I was informed that Sperm whales (Physeter imacrocephalus, Lb.) 
normally remain under water longer than do the ‘ Finners.’ In one 
case a Sperm whale was said to remain submerged for 55 minutes. It 
then came to the surface, gave one long blast, and then shorter and 
shorter expirations until it lay on the surface just breathing quietly. 
As regards the depth of the diving, there seems to be no reason why 
the ‘ Finners,’ which feed on organisms living near the surface, should 
require to swim down to any great depth, as apparently the only object 
in diving must be for food. In the case of the Sperm whales, which 
subsist almost entirely on large cephalopods, a greater depth of dive 
would be necessary in order to reach the bottom-living prey. ‘This is 
confirmed by what has been said above regarding the duration of sub- 
mergence, and it should be noted that the Sperm whales are generally 
found in deeper water. 
In the South in calm weather many Humpbacks (Megaptera longi- 
mana, Rud.) are often found apparently asleep, breathing quietly on the 
surface. 
4. Rate of breeding.—This is not known with any certainty. The 
periods of gestation are probably from about ten months to over a year. 
For Balenoptera musculus (L.) the period is generally supposed to be 
about eleven months,’ and for B. sibbaldii from eighteen to twenty 
months (Guldberg). Breeding appears generally to take place once a 
year, but it is said that in the case of Balenoptera sibbaldii (Gray) it 
is only once in three years. There is almost invariably only one at a 
birth, a twin being very rare among the larger Cetacea. No such case 
occurred during the 1911 season at the Belmullet station. 
" Haldane, Ann. Scot. Nat. Hist., April 1906. 
