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— consider both begin- and final concentration — ') ; the latter 

 cultures with a stronger concentration, compared with other cul- 

 tures. So we see that, when we consider the concentrations, the 

 found intensities of multiplication in sponge and water seem to 

 approach each other. This appears even more clearly, when we 

 compare some intensities in the sponge tissue found in Table 10 

 with the intensities in water with different concentrations of the 

 algae, stated in Table 9. (Here the concentrations have namely- 

 been more accurately established.) We then see that in the sponges 

 3371, 3381, 347, 3701, 416, etc., all of which are sponges with 

 weak concentration of the algae, a multiplication-intensity ruled, 

 which was equal to, even larger than that of the algae in a 

 strong concentration in the water-cultures of Table 9. So this 

 was an indication the more in the above mentioned direction. 



The question was how to compare these concentrations of the algae; 

 so in a culture in water, that is (p. 10) a membrane attached to 

 bottom, and in a more or less green sponge. Of course it is impos- 

 sible to fix the number of algae in equal volumes of sponge and cul- 

 ture. There only remains the comparison of the colour. Thereto 

 one should consider that one can state the colour of the green mem- 

 brane on a white and on a dark background. For a colourless or a 

 green sponge one can say, that the background is white (creamy). 

 Therefore the sponge may be compared directly, as regards its 

 colour, with a membrane on a white (creamy) background. 



Apply this on Table 9. It then appears, that in A the mem- 

 brane in the strong concentration on a white background is yellow- 

 green to light-green, the rim (just as the sponge) dark-green; in 

 the weak concentration the membrane greenish, the rim light- 

 green to green. In B the sponge is dark-green, the membrane in the 

 strong concentration on a white background green to light-green ; in 

 weak concentration the membrane greenish, the rim light-green. 

 Let us now stick to Table 9 A; this one has been continued 

 longest and is the most accurate, as there was no question about 

 infection, as was in the other one. So we see that with a dark- 



1) Nos 3361, 341, 3651, 375, 876 should be neglected as being abnormal. 



6 



