Marshall (1922) stated that: "in those animals in which during immaturity the testicles remain in the body cavity, it is at puberty that these organs first descend into the scrotal sacs". Subsequent work has shown that in the rabbit the growth of testes follows a sigmoid curve, increasing rapidly during puberty (Lipschütz, 1924; Kuboshima, 1951; Gaddum, 1964). Brief reports have been published by Lipschütz (1924) and Davies & Mann (1947) on the endocrine function of the pubescent rabbit testis. The object of the present study was to investigate the time-relationship between the androgenic and gametogenic function of the rabbit testis during puberty.
The rabbits came from the Unit's own closed colony which originated from cross-bred rabbits, and in which males reach a mature weight of 3 to 4 kg at 7 months of age. Weaned rabbits were transferred in groups to colony pens. It was observed that fighting began amongst these animals at 60 days of age and `bucking' (attempts to mount) about 10 days later. At this stage seven bucks were separated and trained to ejaculate into an artificial vagina, and thereafter, ejaculates were collected at weekly intervals until autopsy at 126 days. The following were determined: Volume of semen (seminal gel, if present, was included) ; sperm density, in a haemacytometer; the percentage of live and abnormal spermatozoa, as described by Glover (1960); and fructose and citric acid (Mann, 1964). The main results of semen analyses appear in Text-fig.