Artificial Seawater 



27 



very gently through a tube (A) causes the circulation of water in a 

 small tube (B) in which a portion of a hydroid colony is suspended. 



ARTIFICIAL SEAWATER 



From a physiological point of view seawater is a well balanced solu- 

 tion of mineral salts, virtually all of them existing in the ionic form. 

 Earlier analyses accounted only for the major salts, ignoring other sub- 

 stances present in extremely small quantities. On the basis of the 



■*w 



fr^ 



V 



h 



ra 



ch 



m 



^-= 



- v - •. 



>V r y ; -. ■.■:■•-,,-. ■ ■■>-, v- 



Fig. 32. — The arrangement for filtration 

 and circulation of water. After Cleve, 

 from Hagmeier. F, Fj, funnels forming 

 the upper arms of the siphons; sd, sand; 

 ch, charcoal; L, place air is blown in; 

 U, T, return tube. 



Fig. 33. — A device for aeration 

 and circulation of water in small 

 aquaria. After Hagmeier. A, 

 B, tubes. 



analyses of the samples collected by the "Challenger," Dittmar gives 

 the following composition of the seawater (quoted from Murray and 

 Hjort, 1912) : 



table 1. Composition of seawater (according to Dittmar). 



Grams in 1000 gm. of seawater 



NaCl 27.213 



MgCl 2 3807 



MgSC-4 I0 58 



CaS0 4 l - 200 



K2SO4 °- 86 3 



CaCG-3 OI2 3 



MgBr 2 0076 



So far as the principal constituents are concerned the composition 



