GENERAL CONSIDERATIONS 333 



kindly made his preliminary analysis of the accumulated data on the ossification of the vertebral 

 epiphyses available to me. I am also indebted to Professor J. T. Ruud and Mr Age Jonsgard for 

 interpreting some baleen-plate material. 



Mr A. Style has drawn most of the figures in this paper and Mr A. Madgwick is responsible for 

 some of the photographs. 



In the preparation of this paper I have greatly benefited from discussions with Mr S. G. Brown, 

 Dr R. G. Chittleborough and Mr A. Jonsgard. I should also like to thank Dr Mackintosh and 

 Dr Bargmann for their help at all stages of the work. 



Material 

 Investigations of the breeding biology of whales have to be based on systematic examination of the 

 reproductive organs, and the following routine observations and collections are made when possible 

 by biologists working in floating factories. 



Both sexes 



i . Date, noon position of factory. 



2. Length of whale measured in straight line from tip of upper jaw to notch of tail. 



3. Physical maturity; condition of vertebral epiphyses (Wheeler, 1930). 

 • 4. Baleen plate for examination (Ruud, 1945). 



5. Measurement of blubber thickness. 



6. Observations on diatom film (Hart, 1935), parasites, scars, etc. (Mackintosh and Wheeler, 1929). 



7. Since 1955/56 ear-plugs have also been collected (Purves, 1955; Laws and Purves, 1956). 



Females 



8. Sexual maturity. 



9. Foetus present or absent (uterus searched, or not ascertained). If present sex and length and if possible weight 

 are recorded. 



10. Condition of mammary gland; greatest depth and whether virgin, resting, intermediate, or lactating (Mackin- 

 tosh and Wheeler, 1929). 



11. Collection of ovaries, mainly from mature females (fixed and stored in 10% formalin). 



Males 



12. Measurement of testes and collection of specimen. 



By far the most useful information comes from the ear-plugs and ovaries. In the antarctic pelagic 

 whaling season 1953/54, in addition to the usual routine observations, I made a detailed study of a 

 series of 168 pairs of fin-whale ovaries collected at relatively short post-mortem times (1-14 hr.). The 

 main purpose of this study was an investigation of the variations in the morphology and histology of 

 the corpus luteum and corpora albicantia. Specimens were fixed in formalin, Bouin, Heidenhain's 

 Susa, Zenker-formol and Zenker-formol with post-osmication. One important practical conclusion 

 was that for standard routine examination of whale ovaries some uniform method of slicing was 

 essential and in 1954 a commercial bacon-slicing machine was acquired. With this machine slices of 

 uniform thickness down to 1 mm. can be produced if the material has previously been hardened 

 either by freezing or by storing in formalin. In routine examination 5 mm. slices are cut and all ovary 

 material obtained since 1954 has been treated in this way. 



Between 1934 and 1939 and again from 1945 to 1955 through the kind co-operation of a number of 

 whaling companies annual collections of blue whale (Balaenoptera musculus) ovaries were received 

 and examined. With the decline in the catch of blue whales these collections were decreasing in 

 importance and in the season 1955/56 the whaling companies were asked to collect fin-whale ovaries. 

 The companies' collections for this season totalled 334 pairs of fin-whale ovaries. Date, and position, 



