The Relations between Marine Animai and Vegetable Life. 



351 



In each of these experiments the alga was allowed to act l'or 

 four days. In every case but oue the water was rendered very 

 harmful to the growth of the larvte, as far as size was concerned, 

 but in three out of the four cases the actual number of larvte 

 developing was considerably larger than the normal. Probably the 

 increase in the amount of ammonia present, as determined after four 

 days exposure to the action of the alga, is sufficient to account for 

 the diminished size of the larvai. The organic aramonia seems to 

 exert the most harmful iniluence. Thus in Exp. 95, in which it was 

 179^ greater than that in the normal water, the larvai were 

 diminished by 18.1X- 



Experiments were also made in which the fertilised ova were 

 allowed to develop in contact with the alga. The results obtained 

 are given in the follo wing table. 



In the three experiments made on the effects of red weed alone, 

 the larvai were increased in size in one case by 4.1^, in spite of 

 the fact that, as compared with the water in which larvae had been 

 grown under parallel conditions, but without aiiy alga, there was a 

 large increase in the free ammonia present. It is difficult to account 

 for the larva; in the next experiment, No. 90, being diminished 4.1^ 

 in size, for the ammonia present in the water was altered but little. 

 Probably in the one case the alga was in a healthy condition, and 

 in the other not. In Exp. 92 the alga was obviously unhealthy, and 

 by the end of the eight days it had almost completely changed from 

 a pink to a green colour. 



In that red weeds appear as a rule to increase the amount of 

 free ammonia present in the water, as well as the organic, it was 



