PIGMENT CHANGES IN ANURAN LARVAE 135 



ial melanophores of such larvae expand under the stimulus of 

 light, but the xantholeucophores are not affected, consequently 

 the ' pituitariless' animal remains silvery. 



Many of the agents mentioned exert their influence upon the 

 melanophores through the intermediation of the nervous system. 

 In the transplantation experiments recorded here it is probable 

 that the hormone acts directly upon the melanophores themselves 

 by way of the blood stream, and not through the intermedi- 

 ation of the nervous system, though the latter possibility is not 

 ruled out. However, if, as has been clearly shown by Laurens 

 ('15), other agencies are capable of acting directly upon the 

 melanophores, it is very likely that the hormone of the pars inter- 

 media does likewise. 



It is interesting to note that the secretion of another en- 

 docrine gland, arising as an outgrowth from the dorsal surface 

 of the diencephalon, has a marked effect upon the melanophores 

 of anuran larvae. McCord and F. P. Allen ('17) have clearly 

 demonstrated that the pineal gland of mammalia, when ad- 

 ministered in various ways to anuran larvae, brings about con- 

 traction of the subepidermal melanophores, thus causing the 

 tadpoles to assume a condition simulating the silvery appearance 

 characteristic of hypophysectomized animals. The effects of 

 this gland are temporary and soon disappear. 



Recently the writer transplanted the pineal gland of reptiles 

 (Chelonia) into darkly pigemented larvae of Rana climitans, and 

 obtained rather interesting results. Within thirty to forty min- 

 utes following implantation of the gland into the body cavity, 

 the larvae turned distinctly lighter in color, i. e., from a dark 

 brown to a Hght greenish-yellow. The light color persisted for 

 several hours, when the animals gradually resumed normal col- 

 oration. Mammalian pineal-gland substance (desiccated) in form 

 of pills was injected into the body cavity with similar results. 

 These experiments confirm the previous work of McCord and 

 Allen (F. P.) upon feeding mammalian pineal substance to tad- 

 poles, though the color change following implantation or injection 

 of the gland in my larvae was not nearly so striking as that 

 described by these investigators when the tissue is fed. 



