612 



ECOLOGY AND BEHAVIOR 



shark was removed from the water and sacrificed by transsection of the 

 spinal cord and destruction of the brain. 



Animals were randomly selected for sacrifice. The number of animals 

 sampled and the periods of time in the experimental pens are given in Table 

 1. Samples of kidney, rectal gland, esophagus, stomach, spiral intestine, 

 spleen, gonad, liver, pancreas, and abdominal wall were removed following 

 the sacrifice of an animal. Small pieces (2.5 mm 3 ) of tissue were fixed in 

 either 10% neutral buffered formalin (ph = 6.9 in either seawater or elasmo- 

 branch ringers, approximating the osmolarity of the plasma),* Baker's for- 

 malin (pH = 7, isosmotic), aqueous Bouin's solution (in elasmobranch ring- 

 ers), or Helly's fluid. Sectioning was performed after embedding in paraffin 

 or glycolmethacrylate. 



Frozen sections were made after being embedded in water, Tissue Tek, or 

 10% gelatin. The sections were stained with Sudan Black B, Sudan IV, or 

 Nile Blue A (Humason 1967). 



A qualitative assay for cholesterol in the interrenal gland was designed, 

 using the Microphotoautomat complex of a Wild M-20 microscope (Wild 

 Heerbrugg, Ltd., Ch-9433 Heerbrugg, Switzerland). This apparatus monitors 

 light intensity at the source and at the attached camera; the results are 



Table 1. Number of animals sampled 

 and days in captivity. 



Days in captivity 



Number of 

 animals 



