By Everard L. Napier, M.R.C.S., L.R.C.P. (Lond.). In charge Kala-azar research, Calcutta School of Tropical Medicine. Second edition. 185 pages of text with 15 charts in the text, 18 plates, and an appendix of references to literature, author index and subject index. Oxford University Press. London, Bombay, Calcutta, Madras, 1927
When Australorbis glabratus snails were reared singly from hatching in water-glass aquaria the life span was observed to be about 18 months and the reproductive span was 15–16 months. When 2 or 5 snails were cultured in battery jars with 4 liters of continuously changing water, the life and reproductive spans were, respectively, 6 and 5 months for 2 snails per jar and 8 and 7 months for 5 snails per jar. However, the total number of eggs exceeded that of the water-glass aquaria.
Egg production figures for snails reared singly were 0.6 clutch per snail per day, 38 eggs per clutch, and 23 eggs per snail per day. When 2 snails were maintained per battery jar, the corresponding figures were 1.7 clutches per snail per day, 50 eggs per clutch, and 85 eggs per snail per day; with 5 snails per jar the figures were 1.4 clutches per snail per day, 47 eggs per clutch, and 66 eggs per snail per day. On the basis of the last set of figures the reproductive potential of A. glabratus was about 14,000 eggs.
At temperatures ranging from 22–24°C, the incubation period ranged from 7–14 days with a peak at 8–9 days.
Interrelated with varying environmental conditions, there appears to be an inverse relationship between the rate of egg production and the reproductive span of A. glabratus. Under optimal conditions the reproductive potential was exhausted in 5 months, whereas under less favorable conditions egg output was reduced and the reproductive and life spans extended.