ON THE ZOOLOGICAL STATION AT NAPLES. 



53^ 



From thii'teen experiments with red and yellow light only two experi- 

 ments with the red produced more O2 than the yellow, viz. — 



Diffused light, red and yellow light, all gave larger quantities of Og 

 than the violet glass. From seven expiiiments with the ammouio-cnpric 

 sulphate solution Sehdenia was the only one to give a larger quantity of 

 O2 than produced from the action of yellow light. 



S. dichotoma . 



Diffused 

 Light. 



©2% 



Red. 



Oo% 



Yellow. 

 0.> % 



Violet. 



02% 



28-07 



80-416 



20-994 



26-211 



Sehdenia, after being exposed to violet light, lost its original colour, 

 and turned a pale green. Several algae, after having been exposed to the 

 ■violet light, were killed. The other colours did not destroy so rapidly. 



From the green light of the chlorophyll solution the quantity of 0-2 

 found was very small ; in one case the total quantity of gas given off was 

 only 0-268 c.c. at 0° C, and 760 mm. mercury. 



The next series of experiments were made in order to determine the 

 exact quantity of O2 given off from the same plant under different rays 

 of light. A small quantity of the dissolved gases was removed from the 

 sea water by means of a pump. A portion of the plant to be experimented 

 on was placed in an air-tight flask with some of this water. The O2 

 was determined before and after the experiment by Winkler's method,, 

 the difference being the O2 given off by the plant under experiment. 

 The results varied considerably, the principal cause being due, I think, to 

 the unhealthy state of some of the algse. After some care the results 

 obtained agreed fairly well with those obtained by the first series of 



