Morphological abnormalities of spermatozoa have long been a subject of study, and a small percentage of abnormal spermatozoa is to be seen in most ejaculates. Such abnormalities were first described using light microscopy and later using the electron microscope. In some later studies, specific morphological changes have been clearly demonstrated, e.g. acrosome abnormalities in boar spermatozoa (Bane, 1961; Bane & Nicander, 1966), `knobbed sperm' defect (Blom & Birch-Anderson, 1962) and `pouch formations' in the nucleus (Bane & Nicander, 1965). Some of these changes have been associated with sterility.
This preliminary communication describes changes in the nuclear chromatin of the spermatozoa of infertile bulls which may be of interest in relation to current work on the maturation of nuclear chromatin. The major abnormalities observed were a granular appearance of the nuclear chromatin in a