The Relations between Marine Animai and Vegetable Life. 421 



potassiiim nitrite and potassium nitrato in small quantities bave no 

 action. 



Aeration has only a very slightly favourable effect on larvai growth. 



The nitrites present are greatly diminished on keeping the water 

 in darkness, but are inereased by vegetable growth, and on deve- 

 loi)ment of larvjc in the water. 



The arm lengths are as a mie affected in the same direction 

 as the body lengths on ehange of environmental couditions, but in 

 the reverse direction by water filtered through sand, water exposed 

 to sunlight and water previously heated to 100" C. 



The specific gravity and purity of the Aquarium water vary 

 but little at different times of the year. The salinity is about a 

 hundredth part greater than that of oi)en sea-water. 



Mittheilungen a. d. ZooL Station zu Neapel. BcL 13. 28 



