. 250 200 150 100 0 510 15 2005 O FREQUENCY IO 15 20 Text-fig. 29. Measurements of seminiferous tubules. A, humpback whale, West Australia; B, fin whale, South Africa; C, fin whale, antarctic; D, E, and F, means ± 20- and for antarctic fin whales classified as to diatom infection; D, recent arrivals; E, heavy diatom infection, South Georgia; F, heavy infection, antarctic pelagic. It seems probable then that the fin-whale material from South Africa and the humpback-whale material from Australia has undergone much greater shrinkage than the antarctic material, so that the testis tubule diam
. 250 200 150 100 0 510 15 2005 O FREQUENCY IO 15 20 Text-fig. 29. Measurements of seminiferous tubules. A, humpback whale, West Australia; B, fin whale, South Africa; C, fin whale, antarctic; D, E, and F, means ± 20- and for antarctic fin whales classified as to diatom infection; D, recent arrivals; E, heavy diatom infection, South Georgia; F, heavy infection, antarctic pelagic. It seems probable then that the fin-whale material from South Africa and the humpback-whale material from Australia has undergone much greater shrinkage than the antarctic material, so that the testis tubule diameters cannot be directly compared. It is also possible, however, that the South African material gives a true picture, relative to the antarctic material, and that there is a decrease in average tubule diameter from July to September, followed by an enlargement associated with the southward migration. This possibility is discussed later (p. 453). It seems clear, when the evidence is combined, that there is a very definite cycle of activity in the male fin whale. It should be noted that the bulk of the fin-whale population is in the Antarctic during the months covered by the samples because at this time they must feed in antarctic waters (Mackintosh and Brown, 1956, fig. 2; Marr, 1956). It can safely be assumed that, so far as it goes, the material gives a true picture of the male sexual cycle. The individual rate of regression in tubule diameter is actually greater than Text-fig. 28 suggests, because of the smoothing effect of the continued arrival in the Antarctic of males from lower latitudes. Even in January and February there are some males with seminiferous tubules about 200 p in mean diameter and it seems likely that these are recent arrivals. Is there any way of confirming this? Hart (1935) showed that the presence of a thick diatom film on the surface of the body can be taken to indicate that a whale has been in antarctic waters for at least a month, and conversely, th
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