. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 258 WILLIAM L. ENGELS 100 50 25 10 5 o Immature • Adult + Age Uncertain x "Spring-caught" CO UJ •|- CO LJ o - CO h- X CD 8 8 o • • o. o o o 0 25 i 50 '75 100 i 125 i SEPT. OCT. DAYS OF 14-HR. PHOTOPERIOD NOV. | DEC. | JAN. | FEB. | MAR. FIGURE 1. Recrudescence of bobolink testes, as indicated by weight, when exposed to 14-hour photoperiods beginning in early November. Sloping line indicates a k value of beginning at day 80. The birds were killed by decapitation, the testes removed and fixed in Hell
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 258 WILLIAM L. ENGELS 100 50 25 10 5 o Immature • Adult + Age Uncertain x "Spring-caught" CO UJ •|- CO LJ o - CO h- X CD 8 8 o • • o. o o o 0 25 i 50 '75 100 i 125 i SEPT. OCT. DAYS OF 14-HR. PHOTOPERIOD NOV. | DEC. | JAN. | FEB. | MAR. FIGURE 1. Recrudescence of bobolink testes, as indicated by weight, when exposed to 14-hour photoperiods beginning in early November. Sloping line indicates a k value of beginning at day 80. The birds were killed by decapitation, the testes removed and fixed in Helley's fluid; subsequently, after some time in 70% alcohol, they were weighed to the nearest mg. RESULTS The results are presented in Figures 1 and 2. It will be convenient to con- sider them in three steps: first, the data from the 14-hour photoperiods, next the data from the 18-hour photoperiods and lastly the data from the photoperiods intermediate to these two. 1. 14-hour photoperiods (Figure 1} There is no apparent upward trend in the testicular weights until 84 days after the first 14-hour photoperiod, when one of the four birds shows that recrud- escence has begun, with testes weighing mg. After 114 days the testes of one of four birds are still inactive (only mg), two may have just begun active growth (about 3 mg), while one has reached 80 mg. The final two specimens, killed after 130 days, were both undergoing testicular recrudescence, although the testes of one weighed only mg. The results indicate that the initiation of recrudescence is delayed for several weeks, perhaps ten or more, after the first 14-hour photoperiod. 2. 18-hour photoperiods (Figure 2) The results are in sharp contrast to those of the 14-hour group. Recrudescence apparently began immediately; after only 16 days each of six birds tested had. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
