The Relations between Marine Animai and Vegetable Life. 



385 



than the Dormal, and the other two specimens of water somewhat 

 less; but when the laiTse had reached their full eight days' develop- 

 ment, ali thiee specimens of water were found to eontain more 

 baeteria than the normal. Thus the bacteriological condition of the 

 heated water seems to bave been little if at ali better than that of 

 the unheated. This counting of colonies is, however, unable to 

 distinguish harmful from harmless baeteria, and it is very likely 

 that the heating killed off the most injurious germs, allowing only 

 the harmless ones to subsequentl}^ multiply. 



e. Other Bacteriological Resulta obtained. 



The present seems a favourable opportunity to mention the 

 results of some of the other bacteriological examinations imdertaken. 

 Piate cultures of the normal tank water of the Aquarium gave the 

 following nurabers of baeteria. 



Here we see that after 24 hours' incubation, the number of 

 colonies varied from 510 to 3340 per cubie centimetre, and after 

 48 hours', from 850 to 7160. These numbers are somewhat smaller 

 than one would expect. Thus Sanpelice' found as a rule very much 

 larger numbers of baeteria in various specimens of water coUected 

 dose to the shore of Naples, near the openings of drains, and in 

 the harbours. Out of 96 determinations, the water contained less 

 than 1000 baeteria in 27 cases, and more than 100,000 in 15 cases. 



Of the other bacteriological examinations, the majority were 

 made to determine the effects of filtration through sand more or less 

 impregnated with diatoms and algse. The following results were 

 obtained. 



Boll. Soc. Naturai. Napoli Voi. 3 1889 pag. 33. 



