294 DISCOVERY REPORTS 



3. The largest whales (all females) measured by the Discovery Committee's staff 



were : 



Blue 28-50 m. (93 ft. 6 in.), 



Fin 2 4'5° m - (80 ft. 5 in.), 



Sei 17-10 m. (56 ft. 1 in.), 



Humpback 14*90 m. (48 ft. 11 in.), 



but these lengths must sometimes be exceeded. 



4. An account is given of the few known records of the weights of whales. The 

 greatest is that of a Blue whale of 27-18 m. (89 ft. 2 in.) which weighed about 120 tons. 



5. The average yield of oil obtained by modern whaling methods appears to be about 

 100 barrels from a Blue whale, 50 from a Fin, 40 from a Humpback and 17 from a Sei. 



6. Blue, Fin and Humpback whales in the Antarctic feed heavily and almost ex- 

 clusively on Euphansia superba (the ' krill '). Occasional fish and squids form an insig- 

 nificant part of their diet. All the evidence indicates that in temperate and tropical 

 waters in winter they find very little to eat. 



7. A list is given of the common species of external parasites and the species of whale- 

 bone whales on which they occur. Pennella shows that a whale's blubber has a faculty 

 of ejecting foreign bodies such as whale marks, and it is noted that various parasites 

 provide some evidence of the migrations of whales. A reference is made to the literature 

 on internal parasites. Little is known of diseases in whales. Various growths, tumours 

 and abcesses are found from time to time in different parts of the body, and a few other 

 pathological symptoms and some injuries and abnormalities have been reported. 



8. In the light of additional data some small corrections are made to the original 

 estimates of the mean length at sexual maturity in Blue and Fin whales. 



9. A summary is given of previous investigations on breeding, growth and age. It 

 cannot be doubted that the old corpora lutea of the ovaries last for many years, and there 

 is good reason to believe that they persist as recognizable and countable bodies through- 

 out the life of the whale. It is certain that ovulation is spontaneous and highly probable 

 that whales are polyoestrous. The interval between pregnancies is variable. It is be- 

 lieved that two years is the normal period, but females may occasionally become 

 pregnant again while still nursing a calf, and in many instances the interval no doubt 

 extends to three years. 



10. Growth from birth to sexual maturity was originally estimated to take place in 

 Blue and Fin whales in two years. It is not certain that this estimate was correct, but the 

 recovery of a mark showed that a Fin whale almost certainly grew from birth to sexual 

 maturity in not more than three years, and may well have done so in two. It is possible 

 that this period also is variable. 



11. Methods of age determination are reviewed, but the subject is dealt with only 

 briefly pending full analysis of the data on ovaries. A recently recovered mark showed 

 that the rate of accumulation of the old corpora lutea in one Fin whale cannot have been 

 more than eight in six years, and may have been less. 



12. The statistics of catches provide much information on the stocks of whales, but 



