ZOOLOGICAL AND BOTANICAL ASSOCIATION. 13 



air freely ; this want is first felt by those whose motions are the most 

 vigorous and active. Those in the light are always observed to be 

 more lively than those in darkness ; hence they the sooner fail from the 

 cause in question. Next to the influence of atmospheric air, that of food 

 is the most powerful in the development, not only of tadpoles, but pro • 

 bably of almost all animals. In the absence of food they remain small, 

 and do not become frogs, rarely living beyond eight weeks. It has 

 been already said that light tends to feed them by producing a growth 

 of vegetable matters, and that in the very early state the jelly of the 

 spawn affords them nutriment, but they thrive on animal as well as 

 vegetable diet. 



"With reference to the influence of temperature, I have made no 

 particular experiment, but the observations of HiggiD bottom leave no 

 doubt, that not only the hatching of the ovum (as is the case in the 

 ova of higher animals), but the subsequent development *f the tadpole 

 is considerably accelerated by a heightened temperature. 



The influence of various coloured lights upon animal life remains 

 as an interesting subject for further research. The experiments which 

 I have undertaken upon this subject are incomplete as yet. I shall 

 hope at a future time to make known the results. 



Note. — Since the foregoing pages were written, the very interest- 

 ing paper of Horace Dobell, M. D., " On the Influence of White Light, 

 of the different coloured Rays, and of Darkness, on the Development, 

 Growth, and Nutrition of Animals," has come under my notice. His 

 researches, an abstract of which is published in the Proceedings of the 

 Royal Society, vol. ix., p. 644, were conducted during the years 1855- 

 56-57-58, and the subjects selected were the ova and larvae of the silk- 

 worm, and of the frog. . 



His general conclusions are, that, all other conditions being the 

 same — 1st The ova of insects are not directly influenced in the de- 

 velopment by white light, by the different coloured rays, or by dark- 



2nd. The larvae of insects are not directly influenced in their de- 

 velopment, growth, nutriment, or metamorphosis by white light, by the 

 different coloured rays, or by darkness. 



3rd. The larvae of Batrachian reptiles are not directly influenced in 

 their development, growth, nutrition, or metamorphosis, by white light, 

 by the different coloured rays, or by darkness. 



