Observations were made on 110 Merino rams aged between 1 and 64 weeks. They comprised four groups, the animals of which experienced different rates of growth. The weight of the testes a t any one age varied widely. It was closely related to body weight. This relation was similar in all groups. As body weight increased from 23 to 27 kg, the relative increase in the weight of the testes was much greater than that a t higher or lower body weight. The general histological characteristics of the testes were closely related to their weight, and, like it, to body weight. The tubules were present as solid or but slightly vacuolated cords in all animals which weighed less than 21 kg. Spermatozoa were not seen in the lumen of the tubules in any animal which weighed less than 27 kg, and they were present in all but three of those which weighed more than 28 kg. The relative cross-sectional area of the seminiferous tubules increased directly with the relative increase in the weight of the testes until the testes weighed at least 300 g. The weight of the epididymides was more closely related to the weight of the testes than to age or body weight. Its relation to the weight of the testes varied in the different groups. Irrespective of the age a t which the particular body weight was attained, little separation of the prepuce from the penis had occurred in animals which were lighter than 18 kg, and separation was more or less complete in most animals which were heavier than 27 kg.

No abstract

Observations have been made on the seminal characters, body weights, and plasma vitamin A status of rams fed on carotene-deficient diets, at higher and lower levels of food intake. Carotene supplements were provided for a number of the rams at each level of dietary intake. The seminal characters exhibited a seasonal variation, characterized by a reduction in the total number and longevity of spermatozoa during the summer months. Within this period, a temporary increase in the number of morphologically abnormal spermatozoa occurred in the rams of low plasma vitamin A status, or on the lower plane of nutrition. Plasma vitamin A levels fell more rapidly in the rams on the higher plane of nutrition than in those on the lower plane. Morphological abnormality of spermatozoa attributed to vitamin A deficiency appeared at an earlier date in the high-plane group except when rams with presumably low liver stores of vitamin A were fed on the deficient diets. Vitamin A deficiency, if sufficiently severe, resulted in the appearance of a high percentage of morphologically abnormal spermatozoa in the semen of rams on both planes of nutrition. The addition of pure carotene to the diet prevented or reduced this degree of abnormality.

Body temperatures of logerhead and leatherback turtles recorded during nesting excunions were found to be greater than sea temperatures. Leatherback turtles exhibited greater temperature differentials (5,3 -6,2S 0 C) than logerhead turtles (1,9 -3,22°C). The possibility that leatherback turtles may have a preferred temperature range (30-32°C) as is the case in terrestrial chelonians is discussed. Recordings of exhaled air temperatures suggest that leatherback turtles may employ a countercurrent heat exchange system in the nares in order to conserve body heat.