1918 Miles; on Behavior of Blennies 85 



sensitiveness to temperature changes but without any definite results, due 

 in part to the inactivity of blennies. When a gradient pan, giving a dif- 

 ference of S'^ in 35 cm., was used, no results differing from the control 

 pan could be obtained. It seemed unwise to use much of the limited 

 lime upon these experiments. 



Equal quantities of cold and warmed water were run into the respec- 

 tive ends of the gradient tank and the corresponding temperature kept 

 at 15° and 16° respectively. The individuals were used one at a time 

 and the movements charted to scale, considering the time and direction of 

 movement. Of 4 individuals, 2 came to rest at the cool end, 1 in the 

 center, and 1 at the warm end. Those which once reached an end re- 

 mained there. Cottid fish showed more freedom of movement and reacted 

 positively to the cooler temperature. It is probably true that blennies 

 are not readily sensitive to small differences in temperature. 



Chemical methods 



The chemical conditions in the gradient tank, in which much of the 

 work was done, were controlled by means of the water introduced into 

 the tank from faucets through tubes placed at each end and enclosed by 

 screens. Sea water in good condition was on tap from a storage tank 

 used to supply the laboratory. The inlets to the gradient tank were fitted 

 with "tee" tubes with several perforations which distributed the flow 

 uniformly over the width of the tank. The drain tubes, 4 in number, 

 were situated at the surface and bottom respectively, on each side. They 

 were controlled by 4 pinch cocks. This arrangement, with the added 

 facility of regulating the depth of the tee bars at the inlet, made possible 

 a gradient from 1 end of the tank to the other which M-as reasonably 

 homogeneous in cross section. The usual method was to regulate the 

 inflow at 300 cc. per minute at each end, and introduce the chemical to be 

 used into the riglit hand inflow, regulating the concentration of ions as 

 desired. 



The methods used in the analysis of the samples are standard and 

 give fairly accurate results.* Chlorine was determined by neutralizing 

 with sodium carbonate and titrating with silver nitrate, using potassium 

 dichromate as the indicator. From this method total salinity was easily 

 C()m))uted from standard tables, tlie relative proportion of the chief salts 

 in sea water being about constant. The oxygen was determined by the 

 Winkler method. For carbon dioxide the sample was titrated with N/20 



* TIk' rclialiility nf the Kilvcr iiitrntc sdlutioii used in tlic salinity tests may lio questioned 

 sinrc tlie results (ilitjiiiied sluiw a liiRher dejiree of salinity than others have found in this lecality, 

 but this fact has little signiflcan<'e for the comparative results sought. 



