76 FROM FISH TO PHILOSOPHER 



lowed to dry in a cabinet with a minimal temperature 

 control set at 68° F., and within a month or so it was 

 superficially dry and hard. The choice of mud was a 

 httle precious and in many instances the fish failed to 

 survive simply because we did not know how to make 

 bricks: we overlooked the roots, decaying stems and gen- 

 eral debris of a natural swamp. As the months passed 

 the mud in the jars began to crack, and if the crack 

 penetrated to the cocoon it tore this protective envelope 

 and the fish, exposed to air, dried out and died. But 

 some two dozen estivating fish survived a year or more 

 to become the casualties of physiological investigation. 

 Since accurate metaboHc data could not be obtained 

 while the animal was in the mud, they were removed 

 in the estivating state and imbedded in plaster of Paris 

 with only the nose exposed. Several survived a total 

 period of two years in mud or plaster, and one survived 

 three years of estivation and an additional year of starva- 

 tion after it was returned to water. 



It is clear that the fish trapped in the swamps by the 

 recession of the water in the dry season passes into a 

 state of estivation by a series of responses remarkable 

 for their automatic sequence. As the surface water 

 grows shallow, and while the mud is still soft enough 

 for easy burrowing, the fish squirms into the ooze nose- 

 first and turns upward with the snout just below the sur- 

 face of the water. With further descent of the water 

 level, by its weight and squirming motions it follows the 

 subsoil water down to a depth of a foot or eighteen 

 inches, and its excursions to the water's surface shape 

 a bulbous cavity that opens to the air through a small 

 blowhole. When the water finally drains away, the fish 

 can at last breathe without moving, and it curls up with 

 its tail across the top of its head, covering the eyes. 

 (Figure 7.) Its body is coated with a slimy mucus se- 

 creted by the skin, and as this mucus dries it hardens 

 into a brown, parchmentlike, waterproof cocoon that 



