Part V. Changes in the reproductive organs of the male grey squirrel (Sciurus carolinensis)

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I. Introduction. Both sexes of the grey squirrel show diminished general activity during the winter months and, while there is no true hibernation, squirrels probably sleep during severe weather (Middleton, 1930). In Part IV, Deanesly and Parkes show that sexual activity in the female is limited to the spring and summer, the reproductive organs being quiescent throughout the rest of the year. In view of these facts it seemed probable that the male squirrel would also show seasonal reproductive activity. The present paper deals with an investigation into this question and also with a study of the correlation between the size of the testes and that of the accessory reproductive organs. From the material it is evident that there is no regular seasonal cycle in the reproductive organs of the male squirrel, which considered as a species, therefore, has no “ anoestrus.” The possibility that individual males may experience temporary periods of inactivity cannot be excluded, but there is no doubt that the great majority of inactive animals are prepubertal. Therefore size changes in the testis, in its constituent parts, and in the accessory organs, are considered to represent initial growth