The ovaries of female cottonmouths examined revealed ova in various stages of development. In individuals less than 300 millimeters in snout-vent length the ovaries are almost completely undeveloped; in immature individuals from 300 to 450 millimeters in length the follicles are from one to two millimeters in length; in post-post females follicles vary in size, the largest being about seven millimeters. Reproductive females also contain follicles of various sizes. One or two sets are less than three millimeters in length, and large ova that soon are to be ovulated are present. Ovarian ova found in April ranged in length from 23 to 35 millimeters. No embryonic development was observed in most individuals until June or later. TABLE 8.--Percentage of Gravid Females of _A. p. leucostoma_ in 50 Millimeter Size Classes. ===================================== |Snout-vent |Number |Total |Percentage| | | of |number| | | length |gravid | in | gravid | | |females| size | | | | |class | | |-----------+-------+------+----------| | 450-499 | 3 | 14 | 21.4 | | 500-549 | 7 | 17 | 41.2 | | 550-599 | 8 | 17 | 47.1 | | 600-649 | 5 | 7 | 71.4 | | 650-699 | 2 | 9 | 22.2 | | 700-749 | 2 | 3 | 66.7 | | 750-799 | 1 | 1 | 100.0 | | 850-899 | 1 | 1 | 100.0 | | Totals | 29 | 69 | 42.0 | ------------------------------------- Increase in length of testes appears to be correlated with length of the individual rather than cyclic reproductive periods (Fig. 4). The reproductive cycle in cottonmouths resembles that illustrated by Rahn (_op. cit._:237), in which the ovarian follicles of post-partum females begin to enlarge in late summer and autumn, with ovulation occurring the following spring. By means of retaining sperm successive broods possibly are produced after only one mating. In captivity, at least, some females may not follow this biennial cycle; Stanley Roth (M.S.), biology teacher in high school at Lawrence, Kansas, had a female of _A. p. piscivorus_, from Florida, that produced broods of 14 and 12 young in two consecutive years. [Illustration: FIG. 4. Length of testes in cottonmouths of various sizes (·--left; º--right). The right testis is always longer than the left.] Embryonic Development