184 



III. Supplement to a Paper, read February 17, 1859, " On the 

 Influence of White Light, of the different Coloured Rays 

 and of Darkness, on the Development, Growth, and Nutri- 

 tion of Animals*/' By HORACE DOBELL, M.D. &c. 

 Communicated by JAMES PAGET, Esq. Received Sep- 

 tember 23, 1859. 



The apparatus used in the following experiments, was described in 

 my Paper ; but in the present instance, only two of the cells were 

 employed, viz. that exposed to ordinary white light, and that from 

 which all light is excluded. In order more effectually to prevent 

 the possible admission of light, the following precautions were adopted 

 with the dark cell : 1. The perforated zinc floor was covered with 

 thick brown paper. 2. The under surface of the lid was lined with 

 black cloth, to secure accurate adjustment when shut. 3. The 

 opaque black glass was covered with an additional coat of black oil- 

 paint. 4. The lid was never opened in any light except that of a 

 candle or of gas. 



March 20th, 1859. A number of ova of the Silkworm (Bombyx 

 mori), all of the same age, were placed in each of the two cells. No 

 change was observed until May ISth (sixty days after the commence- 

 ment of the experiments), when one larva emerged from the ovum 

 in each cell ; and during twelve days, larvae continued to emerge in 

 the light and in the dark at the same rate. 



June 9th. Sixteen larvae, as nearly as possible of the same size, 

 were selected in each cell, and the rest removed. The experiments 

 then proceeded with these thirty-two individuals, and no death 

 occurred from first to last. 



* Proceedings of the Royal Society, vol. ix. p. 644. 



