646 



"All other conditions being the same, (\.)The Ova of Insects 

 are not directly influenced in their development by white light, by 

 the different coloured rays, or by darkness. 



" (2.) The Larvae of Insects are not directly influenced in their 

 development, growth, nutrition, or metamorphoses by white light, 

 by the different coloured rays, or by darkness. 



" (3.) The Larvce ofBatrachia Reptiles are not directly influenced 

 in their development, growth, nutrition, or metamorphoses by white 

 light, by the different coloured rays, or by darkness. 



" (4.) The Materials necessary to the Colour of Insects and Rep- 

 tiles are prepared equally under the influence of white light, of the 

 different coloured rays, and of darkness." 



These results are so opposed to preconceived ideas upon the sub- 

 ject to which they relate, that they cannot fail to excite some surprise 

 and incredulity ; when, however, they are carefully considered, they 

 assume a theoretical probability, which assists us in believing that 

 the practical results are without fallacy. 



(a.) With regard to the development of the ovum, when we con- 

 sider the unity of plan which appears to preside over the germs of 

 the simplest and of the most complicated forms, and the infinite 

 variety of external conditions in which these germs are placed 

 throughout the animal kingdom, we are led to the conclusion that 

 their development must be so arranged as to be independent of the 

 direct influence of light. 



(b.) That after emerging from the ovum the animal is not di- 

 rectly influenced by light, is more difficult, at first, to believe, be- 

 cause experience seems to have taught us that "to live without 

 light is to live without health ;" but this familiar fact may be at 

 once disposed of in the argument and explained by its coincident, 

 that, under ordinary circumstances, the admission of light is in- 

 separably connected with, 



1 . The regulation of external temperature. 



2. The free circulation of a respiratory medium. 



3. Those processes of vegetable life and of inorganic change 

 upon which the proper condition of the respiratory medium 

 depends. 



Speaking generally then, it must be admitted that light is essential 

 to the development, growth, and nutrition of animals, but only in- 



