The seasons in a tropical rain-forest (New Hebrides). Part 7 (Final part). Summary and general conclusions.

Summary. The following is an attempt to summarize this paper, which is itself a summary: — The vicinity of Hog Harbour, 15°S. in the New Hebrides, Pacific Ocean, was chosen for a study of the breeding seasons of vertebrates in a particularly unvarying tropical rain-forest region. The mean temperature of the hottest month is only about 2°C. higher than that of the coolest, and there is no dry season (though one part of the year is wetter than the other). The animals chosen for intensive study were a fruit-bat (Pteropus geddiei), an insectivorous bat (Miniopterus australis), a passerine bird (Pachycephala pectoralis) and a lizard (the skink, Emoia cyanura). Pteropus, Miniopterus and Pachycephala each had one breeding season during the year of observation. The main period of fertilization of ova was February and March for Pteropus, early September for Miniopterus, and July for Pachycephala. Emoia bred throughout the year, but much more rapidly during November and December than during May and June. It is almost certain that the breeding seasons are annually recurrent. It is certain that increasing length of day does not stimulate the growth of the testes of Pachycephala. From their minimum size in December the testes grew larger by regular monthly increments throughout the period (January to June) during which the days were growing shorter; and while the days were growing longer from October to December, the testes were shrinking to less than one-fortieth of their maximum size. Miniopterus hangs throughout the period of daylight till about ten minutes before sunset in a dark and almost thermostatic cave situated in one of the most unvarying climates in the world, but it did not fertilize its eggs throughout the year of observation except during a few days about the beginning of September, when most of the adult females suddenly became pregnant. It seems probable that the breeding seasons of the animals investigated arc regulated by some altogether unsuspected cause or causes.