390 Canadian Record of Science. 



quality of the water appears to have no influence in prolonging the 

 life of pathogenic bacteria. 



The general conclusions drawn by the author are that the quan- 

 tity of bacteria present in spring water is no guide whatever in 

 determining the wholesomeness or otherwise of the water for 

 drinking purposes, since they are most entirely harmless, and that 

 it is impossible by chemical analysis to determine the presence of 

 bacteria in larger or smaller numbers. The presence of specific 

 pathogenic bacteria can only be determined by direct nicro-che- 

 mical observation. 



How Mykiapods are Affected by Light. — F. Plateau has recently 

 investigated the extent to which Myriapods, both those that are 

 blind and those possessed of eyes, can distinguish a lighted from a 

 shaded spot. He" resorted to various contrivances to graduate the 

 quantity of light and shade, and to have the one sharply marked off 

 from the other. It was also necessary to provide against the danger 

 of fallacy from the influence of heat rays — which was accomplished 

 by placing in the path of the incident rays a flat-sided glass vessel, 

 containing water which absorbed the heat, but allowed the light to 

 pass. After many experiments, he draws the following conclusions : 



1. Myriapods which are blind, perceive the light of day and know 

 how to discriminate between light and darkness. 



2. In both those with and those without eyes, a certain time 

 must elapse before they can perceive whether they are in shadow 

 or iD light. 



3. The duration of this latent period is not longer in the blind 

 than in those with eyes. 



1. When a shaded area is relatively small to the lighted one, 

 they do not practically distinguish between the two. 



5- Myriapods like moisture, and this explains also why they seek 

 shady places, habitually. 



These conclusions are interesting, inasmuch as they show that 

 animals may be affected by light apart from those sensations which 

 are visual strictly so called, and that such changes as light thus 

 produces so influence the nervous system that the animal gets in- 

 formation of a valuable kind as regards ,its life interests. Such 

 experiments as these enable one to understand in some measure, 

 perhaps, that beginning of vision which exists in creatures possess- 

 ing only pigmented spots, as eyes, the pigment in some way 

 retaining the light while it works changes, probably chemical, in 

 the protoplasm. 



Digestive Ferments in Plants and Animals. — It is very interest- 

 ing to the physiologist to note how many processes, once thought 

 to be characteristic of animals, are being shown to be common to 

 plants and animals alike. The researches of Heidenhain and 

 Langley had demonstrated the stages in the cells of digestive glands 



