Marine Aquaria 23 



In another type of arrangement (Fig. 27) the outside arm of the 

 siphon is inserted in a small glass cylinder. A glass tube passing through 

 the bottom serves as an overflow controlling the level in the tank. The 

 instrument may easily be made from a large test tube by cutting off its 

 bottom and inserting two rubber stoppers. A hole in the upper stopper 

 serves for the escape of air. 



The following arrangement (Fig. 28) permits a careful regulation 

 of the rate of flow of filtered water through a series of culture vessels. 



Fig. 28. — The arrangement used in rearing marine larvae. A, reservoir tank; B, C, D, 

 E, culture jars; F, funnel with cotton filter; L, overflow siphon controlling the level 

 of water in the funnel; S, overflow siphon controlling the level in culture jars. 



Tall cylindrical jars with wide lips are very convenient for this purpose. 

 To insure a constant flow the water is first filtered through cotton (F) and 

 siphoned from the tank (A), which is always kept full by means of an 

 overflow siphon (L). The first jar (B) serves only as a supply reser- 

 voir for the others (C, D, E) which are connected to one another by 

 siphons. The jars are placed on boards of various thicknesses so that 

 in each of them the level of the overflow (the lip of the jar) is gradually 

 increasing from left to right. An automatic siphon (S) controls the 

 level of water in the last jar. By this arrangement water gradually passes 

 from (A) through all other jars and is discharged by the siphon (S). 

 Should the latter become clogged, the water in the first jar rises and 

 overflows before the culture jars, standing slightly above it, become full. 



