little difference in the appearance of the male and female gonads and ducts until towards the end of the juvenile males' first hibernation.

The smallest lizard with sperm in the epididymis, collected on July 21, 1954, and 45.5 mm in snout-vent length, was by estimate at least 18 months old. Two other lizards 49.0 mm collected in October, and 46.5 mm collected in November, were not mature. In general, males were at least 51.0 mm from snout to vent before sperm was found in the epididymis. This size is attained towards the end of their second summer before hibernation, when the skinks are by estimate 16 to 17 months old and as no growth occurs in this period the probable time of maturity is on emergence from hibernation when the skinks are 20 to 21 months old.

The adult winter testes range in size from 3.5 mm to 4.5 mm long, 1.9 mm to 2.75 mm wide and 2.0 to 8.0 mgm in weight. The testes of adult animals in the summer months are from 4.0 to 5.5 mm long, 2.2 to 4.25 mm wide and 8.0 to 32.0 mgm in weight. Thus the testes of adult lizards are less in weight and size, particularly in diameter, during the winter months.

Text-fig. 5 shows the testis weight as an average for both testes, for twenty-five specimens of Leiolopisma zelandica and six Leiolopisma aeneum, plotted against the time of the year. The testes are at their minimal mass during June and July, the middle of the hibernation period. Collections during September and October contained too few males to establish the exact time of increase in testis mass, though skinks collected in September and October showed that there is some increase in testis size and weight. From January to April the testes averaged greater in weight than testes from lizards collected during the hibernation period.

From January to June the males 51.0 mm or more in snout-vent length contained sperm within the epididymis. In July, two large adult males contained no sperm, one only a small amount, and three other lizards abundant sperm. Only six lizards, four of which were sub-adult, were examined in September, October and November, and none of these showed sperm in the epididymis, although the testes were of mature size. Text-fig. 6 gives the overall picture of the male cycle, and its relation to the female cycle.

Copulation would be expected to occur at the time of, or shortly after, sperm production in the males and about the same time as ovulation in the females. Ovulation takes place in the first weeks of October, a time which apparently does not coincide with the presence of sperm in the epididymis of the males, as shown in the graph (Text-fig. 5), though it does appear to coincide with a rapid increase in testis size. Copulation has not been observed in the field, and the only copulation seen occurred between two lizards held in the laboratory on March 28, 1955. The attitudes assumed in copulation are shown in Text-fig. 7. The copulating lizards were two of eight that had been caught some 48 hours previously, and placed in a glass trough prior to release, and the copulation may have been a displacement activity, the product of the close confinement and the abnormal conditions to which the lizards were subjected. However, as both this observed copulation and the presence of abundant sperm in all males at this time could indicate that copulation takes place in the late summer, smears were taken from the vents and oviducts of the females collected for the next five months, from early April to late August. No sperm was found in any of these smears, but as they were made from preserved material the results cannot be regarded as conclusive.

From the above data it can be seen that examination of male lizards does not allow the time of copulation to be precisely determined. Either copulation occurs about the time of ovulation in the females, thereby coinciding with the rapid seasonal increase in testis mass, or else copulation precedes hibernation and females retain sperm until ovulation in the following spring, as do certain salamanders (Stebbins, 1954).

Female skinks are not known to retain sperm for lengthy periods before ovulation. Studie on Eumeces fasciatus by Fitch (1954) and Eumeces septentrionalis