METHODS 28s 



included a section on foetal growth, based on 580 fin whale foetuses and 276 blue whale foetuses 

 whose lengths were recorded by trained Norwegian observers in the Antarctic season 1939 '40. This 

 author's conclusions were in very close agreement with those of Mackintosh and Wheeler (1929) 

 concerning the shape of the growth curve for the 4 months, December to March. He showed that 

 for the first 2 months the figures given by the International Whaling Statistics and by Risting (1928) 

 are higher, probably because small foetuses have been overlooked. 



Zemskiy (1950^) studied the relation of length to weight in 100 antarctic fin whale embryos and 

 concluded that there were two distinct stages of development characterized by differences in the ratio 

 of length to weight. He also showed that there is no change in body proportions over a range of 

 lengths from 50 to 565 cm. This work will be discussed below. 



Jonsgard (1951) discussed the foetal length records available to him for the minke whale (B. acuto- 

 rostrata Lacepede) and drew attention to the probable effects of differential migration of pregnant 

 females on the apparent curve of foetal growth. 



Post-war observations by Japanese workers are recorded in several papers which deal in aggregate 

 with some thousands of foetal lengths (Mizue and Jimbo, 1950; Nishiwaki and Hayashi, 1950; 

 Nishiwaki and Oye, 1951 ; Mizue and Murata, 1951 ; Ohno and Fujino, 1952; Omura, 1953; Sakiura, 

 Ozaki and Fujino, 1953; Kakuwa, Kawakami and Iguchi, 1953; Omura and Sakiura, 1956). The 

 results of this work endorsed previous conclusions, particularly the work of Mackintosh and Wheeler 

 (1929) on blue and fin whales. All these authors were content to draw in curves by eye, without 

 attempting to obtain a mathematical fit to the points. Another important paper on twinning and 

 multiple foetuses in southern fin whales, dealing in part with foetal growth, was contributed by 



Kimura (1957). 



Reference must be made to a short paper by Frazer and Huggett (1958), based on foetal lengths 

 included in the International Whaling Statistics. They conclude that the gestation periods of sperm, 

 humpback, fin and blue whales are respectively 15-16, 12, 9-10 and 9 months. They state that other 

 data suggest that the pilot whale, Globicephala melaena Traill, has a gestation period of 16 months. 



So far we have been concerned mainly with the baleen whales {Mysticeti). The material available 

 for a study of foetal growth in the toothed whales {Odontoceti) is much less abundant. The principal 

 papers are those by Guldberg (1894) on four species of odontocetes, by Matthews (i938«), Mizue and 

 Jimbo (1950) and Clarke (1956) on the sperm whale; papers by Degerbol and Nielsen (1930), Vladykov 

 (1944) and Doan and Douglas (1953) on the white whale {Delphinapterus leucas Pallas); and an 

 important work by Mohl-Hansen (1954) on the porpoise {Phocaena phocoena Linn.). The full results 

 of recent work on the pilot whale {Globicephala melaena Traill) are not yet available (Frazer and 

 Huggett 1958; Sergeant, unpublished; Ann. Rep. Fish. Res. Bd Can., 1954). There are other papers 

 which give less complete information about the course of foetal growth, and estimates of the length 

 of gestation, size at birth, etc., for several species. 



Finally it should be mentioned that Scott (1949) has shown that for ten cetacean species the average 

 neonatal length is directly correlated with adult length (which he defines as an estimate of the 

 maximum length generally attained). 



METHODS 

 Most of the data which are available for different species are sufficient to fix the rates of foetal growth 

 for only part of the gestation period. For the southern fin whale in particular the bulk of the records 

 cover the 6 months October to March, the first two of these months being poorly represented (Text- 

 fig 9) For some other species the data are perhaps rather more widely spread in time, or cover an 

 earlier part of gestation; for example, the humpback whale, the minke whale, the sperm whale and 



