The morphology of the spermatozoon from the cauda epididymides of representative members of both subfamilies of squirrels, the Sciurinae and Callosciurinae, is described. It has been found that in all species some variability of sperm form occurs within in all individuals but there is invariably a massive apical segment of the acrosome that varies in the extent of caudal flexion.
It is suggested that these findings may reflect movement of the acrosomal apical segment during sperm transport and it is possible that this may facilitate migration of the sperm up the female reproductive tract to the site of fertilisation.