INSECTS EMPLOYED IN MEDICINE, OE AS EOOD. 109 



Later still, M. Berard took a certain quantity of 

 eggs of the fly (Musca Ocesar) ; lie divided them 

 into separate groups, and placed them under different 

 coloured glass jars. In four or five days, the larvce 

 produced under the blue and violet coloured jars 

 were much larger and more fully developed than 

 the others : those hatched under the green jar were 

 the smallest. The blue and violet jars were found, 

 therefore, to be most favourable to rapid and com- 

 plete development ; then came the red, yellow, and 

 white (transparent) jars ; and last of all the green. 



The larvce developed in a given time under the 

 influence of violet light were more than three times 

 as large as those hatched and reared in green 

 light.* 



The experiments are certainly very interesting 

 in a practical point of view ; for if it be true, as it 

 appears to be, that the larger a silkworm is the 

 more silk it will produce, it would be worth while to 

 repeat these experiments upon silkworms, and en- 

 deavour to raise a large breed under violet glass. 



* The effects of the sun's rays, when filtered through differently 

 coloured glass, upon the development of infusorial life, has recently 

 occupied Mr. Samuelson. He fitted up a box containing three 

 compartments, covered by a pane of blue, red, and yellow glass 

 respectively, and found that under the blue and red glass infusoria 

 were rapidly developed, whilst under the yellow hardly any signs of 

 life were visible. He then transferred a portion of the infusion 

 from the yellow to the blue compartment, when infusoria very soon 

 made their appearance. 



