After referring to the experiments of Edwards, Higginbottom, 

 E. Forbes, Morren, Wohler, Hannon, Moleschott, and Beclard, the 

 results of which were shown to be somewhat contradictory, the 

 author described the precautions taken by himself to avoid sources 

 of fallacy. 



The original experiments detailed in this Paper were conducted in 

 the years 1855, 1856, 1857, 1858. The subjects selected were the 

 Ova and Larvae of the Silkworm (Bombyx mori) and of the Frog(7to# 

 temporaria). A comparative experiment in the vegetable kingdom 

 was also made on the Sweet Pea (Lathyrus odoratus). An appa- 

 ratus contrived for the experiments on Tadpoles was described and 

 figured ; it secured the following desiderata : 



1 . That each of six compartments or cells should be supplied with 

 water from the same source, at the same time, subject to the same 

 changes, and capable of being refreshed without' interfering with the 

 cells. 



2. That each of the cells should be placed in the same condition 

 with respect to the supply of air and of food. 



3. That during exposure for examination of the animals, the 

 whole series should be opened the same length of time and to the 

 same extent. 



4. That each cell should receive no light but that transmitted by 

 its proper cover. 



One of these six cells was open to the air and to light ; one was 

 covered with ordinary white glass ; one was made completely dark 

 by a covering of blackened opaque glass ; one was covered with blue, 

 one with greenish yellow, and one with red glass. The transmit- 

 ting and absorbing powers of these glasses were detailed from expe- 

 riments made upon them by Mr. Cornelius Hanbury, jun., and by 

 the author. 



The apparatus used for the Silkworms was, in all essential par- 

 ticulars, the same as that for the Tadpoles, only without water. 



A tabulated analysis of the daily journal kept during the experi- 

 ments was given, and its separate items compared and discussed ; 

 after which the author concluded his Paper with the following resume, 



" If we may venture to reason on so small a number of observa- 

 tions, so far as the results of these experiments are concerned, the 

 following propositions may be advanced. 



2 x2 



