112 E. E. HOSKINS AND M. M. HOSKINS 



because some escaped with bile into the intestine. The neutral 

 red in the urine appeared to be in solution when examined under 

 the microscope, whereas some, at least, of that in the bile was in 

 granular form. Before the filtered neutral red was injected it 

 appeared to have only very minute granules, smaller than those 

 in the bile, so that in passing through the liver, granules must 

 have collected together. Denis ('12) found the urine acid to 

 litmus, but neutral red excreted in it retained its red color. 



C. Congo red. The Congo red used could easily be removed 

 by filtration or setthng and would not pass through a celloidin 

 membrane. 



1. Two adult dogfish received intravenously each 5 cc. of a 

 heavy suspension of Congo red in sea-water. After twelve 

 hours the urine was still free from the dye, as was the stomach 

 and spiral- valve contents. A considerable amount was present 

 in the bile. 



2. A young fish (0.25 kg.) received doses of Congo red of 12 

 cc. and 18 cc, respectively, on two successive days and was 

 autopsied forty-eight hours after the first injection. The liver 

 and spleen were stained deeply with the dye, but the other 

 organs of the body cavity appeared practically normal in color. 

 The gills were not examined. A large amount of the dye was 

 present in the bile, a small amount in the spiral valve, and a 

 trace in the stomach. The dye in the spiral valve entered with 

 the bile probably entirely and that in the stomach probably was 

 regurgitated from the spiral-valve. 



D. Trypan blue. ' Trypan blue was used primarily in studying 

 the excretory function. Its action as a vital stain, although 

 not exhaustively studied, will be considered also from the data 

 we have, because the reaction in selachians seems to be in some 

 ways different from that in teleosts as described recently by 

 Wislocki ('17). A brief review of our results with this dye has 

 been published (Hoskins and Hoskins, '18). 



1. An adult male was injected intravenously with 9 cc. of a 

 § per cent suspension of filtered trypan blue in sea-water. Four 

 hours later the animal received 6 cc. more. Fifteen hours later 

 another injection of 6 cc. was made. Autopsy was performed 



