THE PITUITARY BODY 



assay inasmuch as the female Phoxinus, although only 6 

 cm. long, may or may not respond depending upon the con- 

 dition of the ovaries. According to Wunder (1931) a typical 

 "wedding dress" can be produced in the Bitterhng by the in- 

 jection of a testicular extract but not by the injection of 

 oestrin. Abolin was impressed by the variable response of the 

 chromatophores of Phoxinus. 



The ejects of hypophysectomy or of extracts of the pituitary 

 on the chromatophores of amphibia, i. Anura. — The effects of 

 hypophysectomy on the chromatophores of tadpoles were 

 first observed by Allen (1916) and Smith (1916). (See chap, 

 ii, pp. 39-40.) The appearance of the hypophysectomized in 

 comparison with the normal frog tadpole is shown in Figure 

 45.^ The most striking changes consist of a concentration of 

 the melanosomes, particularly in the melanophores of the 

 epidermis, and a dispersion of the pigment granules in the 

 xantholeucophores. Both of these changes are responsible 

 for the silvery (albino) appearance of hypophysectomized 

 tadpoles. It is also agreed that the amount of free melanin in 

 the epidermis is reduced. According to Smith (191 6, 1919- 

 20) hypophysectomy in the tadpole is also followed by a 

 reduction both in the amount of intracellular melanin and 

 in the number of the epidermal melanophores. This has been 

 questioned both by Allen (1917) and by Atwell. According 

 to Atwell (1919, 1921), the melanosomes are also concen- 

 trated in the deep-lying melanophores; however. Smith ob- 

 served no change either in these cells or in the retinal pigment 

 cells. Smith found that the transplantation of the skin from 

 a hypophysectomized to a normal tadpole was promptly fol- 

 lowed by a return of the pigment granules of the xantho- 

 leucophores from the dispersed to the concentrated state. 



Hypophysectomy in frogs or toads is likewise followed by 

 a concentration of the melanosomes and a dispersion of the 



* It appears that not all the pars buccalis was destroyed in Adler's tadpoles 

 (Fig. 43)- 



[306] 



