Further Observations on the Dag-Defect of the Tail of the Bull Spermatozoon

Summary. Changes were found in the tails of the spermatozoa from a 1½-year-old Jersey bull which conformed to the previously described Dag-defect. The tails were heavily coiled so that transverse sections contained several axonemal units enclosed in the same common cell membrane. The axonemes were abnormal, as one or more of the doublets with the corresponding matrix were lacking, and usually the half of the axoneme containing Fibres 4, 5, 6 and 7 was affected. The central fibres and outer coarse fibres were often affected as well. These changes were generally found in close relation to remnants of the cytoplasmic droplet. In the testes, the spermatozoa were morphologically normal and the changes described seemed to originate in the distal part of the caput epididymidis. The possible aetiology and pathogenesis of the defect are discussed.