. Discovery reports. Discovery (Ship); Scientific expeditions. THE REPRODUCTIVE ORGANS 407 in length, the age or size of the whale evidently ceases to be the factor which dominates the size of the testis, and other factors must be sought in order to explain the great variations in its size in large whales. In the porpoise the testis is described by Meek (1918) as undergoing an enormous development in the summer (northern hemisphere), the breeding season being in July and August, and it is natural to suppose that some- thing similar might occur in the Balaenopteridae. If this were so the size o
. Discovery reports. Discovery (Ship); Scientific expeditions. THE REPRODUCTIVE ORGANS 407 in length, the age or size of the whale evidently ceases to be the factor which dominates the size of the testis, and other factors must be sought in order to explain the great variations in its size in large whales. In the porpoise the testis is described by Meek (1918) as undergoing an enormous development in the summer (northern hemisphere), the breeding season being in July and August, and it is natural to suppose that some- thing similar might occur in the Balaenopteridae. If this were so the size of the testis might provide a valuable clue to the period and duration of the breeding season. Unfortunately, however, there is no evidence that this is the case. If the testes of all the sexually mature whales are plotted, according to the time of year and volume of the testis, there is no indication of any correspondence between the two. The great diversity in the size of the testis in different whales might be accounted for if there is considerable individual variation and at the same time a slight increase in size in answer to a stimulus associated with breeding. The most instructive observations on the testis are those made from the histological point of view. One of the most striking features of the testis is the extraordinarily small number of spermatozoa which are normally to be seen in sections, and it may be said at once that the examination of sections gives no support to the supposition that the testis might undergo any important increase in size when breeding takes place, for the largest testes appear to contain no more spermatozoa than the smaller. Sections of the immature testis (Fig. 140) show small tubules, of which the wall consists of a layer of small cells with small, strongly staining nuclei. The lumen of each tubule is completely filled by a comparatively small number of large cells with large nuclei which do not stain very strongly and of which only about
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectscientificexpedition
