The Relations between Marine Animai and Vegetable Life. 



381 



e. The EflFect of Filtration through Asbestos. 



In some of the ubservations to be subseqiiently described, it 

 was necessary lo filter off the larvse from the water in which they 

 were growing. This was (Ione by plugging up the bottoni of a fimnel 

 with a layer of asbestos about a centimetre in thickuess, and letting 

 the water ruu through. It was aecordingly thought advisable to 

 determine whether the filtration itself could bave any effect on either 

 the cheuiical composition of the water, or on the growth of the larvse. 

 The following results were obtained. 



From these figures one may see that whilst the free ammonia 

 present in the water was only slightly affected, the organic ammonia 

 was considerably increased in amount. This could ßcarcely bave 

 been due to any soluble impurity in the asbestos itself, for half a 

 litre or more of water was allowed to tìlter through before a specimen 

 was collected. It can only be concluded that the process of filtration 

 itself causes the increase. It may be that the particles of solid organic 

 matter in the water become caught by the asbestos fibres, and broken 

 up and decomposed by the stream of water running through them. 



Strange as is the effect on the chemical composition of the water, 

 that on the growth of the larvse is much more remarkable. Thus in 

 one instance they were increased in size by no less than 22.8^! 

 On the other band upon the actual number of fertilised ova reachiug 

 full larvai development, the filtration has either no effect at ali, or 

 a slightly adverse one. In the last experiment given in the table, 

 the larvse were grown in a specimen of water which had been filtered 

 through asbestos, and then kept 25 days in darkness. The increase 

 in size is 7.4^, whilst with larvse grown in some of the same water, 

 which had also been kept in darkness under the same conditions, 

 but which had not been filtered through asbestos, the increase was 

 only 4.2^, or "6:2% less. 



