DEPARTMENT OF EXPERIMENTAL EVOLUTION. 123 



per cent over that in the egg. The greatest loss is from the protein 

 fraction, some of which has gone into the fat. Dr. Gortner concludes: 



"There is considerable evidence that the nitrogen ratios in the protein fraction 

 are not fixed quantities, but that some amino acids are more necessary for the 

 development of the embryo than are others, and as a result there is a continuous 

 breaking down and recombining of the resulting radicals into new compounds. 

 For example, the gain observed for arginine B, although small, is probably 

 significant. It seems probable that there is, in the eggs of Cryptobranchus, a 

 carbohydrate nucleus, either free (glycogen) or combined in the form of a 

 glycoprotein, and that during the process of embryonic growth this carbo- 

 hydrate is broken down to carbon dioxide and water, with a consequent libera- 

 tion of energy for the 'Entwicklungsarbeit;' but the breaking down of the 

 carbohydrate proceeds more rapidly than the needs of growth demand, with 

 the result that the surplus energy is stored as fat." 



Inhibition of Pigmentation, A. M. Banta. 



In the last two reports attention has been called to our w^ork in 

 preventing the formation of black pigment in the little salamander, 

 Spelerpes, by phenols. This year Dr. Banta used the same method 

 with young larvae of the giant salamander, Cryptobranchus, and got 

 practically the same results. When small amounts of these inhibitors 

 to the oxidation of tyrosin (a process which forms black pigment) are 

 put into the tissues of the developing larvae before pigmentation 

 begins, the onset of pigmentation is markedly postponed and the 

 pigment produced is much reduced in amount. Because of the toxicity 

 of the inhibitors it is impossible to state how long these modifications 

 would persist, for the larvae, even though kept in the solutions for only 

 8 to 15 days, do not develop beyond the stage when the stored food in 

 the egg is all utilized. 



A Toxin of Bread Molds, R. A. Gortner and A. F. Blakeslee. 



In last year's report the discovery (made in the course of studies on 

 sex of molds) of a powerful toxic agent in the bread mold, Rhizopus 

 nigricans, was alluded to. The full paper has now been published. 

 The toxin has no effect when taken into the alimentary tract by a 

 rabbit, whereas it is fatal to rabbits when injected intravenously in 

 even so small an amount as 1 to 275,000 parts of body-weight, being 

 one of the most poisonous organic substances known. 



Modifying Effects of Cave Conditions, A. M. Banta. 



The material in the cave and vivarium has been brought through 

 with greater success than in any previous year. To the species pre- 

 viously maintained here have been added the blind cave-fish, Amhly- 

 opsis spelceus, and an additional species of salamander, Amby stoma 

 opacum. During the present season large series of wood-frog tadpoles 



