August 25, 1916] 



SCIENCE 



281 



This epithelial ingrowth was removed with 

 some neighboring epithelium. The wound 

 healed within three hours, less than 1 per cent, 

 of the larvas disintegrating after the operation. 

 About 200 larvae of the 3 mm. stage were oper- 

 ated upon, the hypophysis being successfully 

 removed in over 60 per cent, of the cases. Ap- 

 proximately 30 per cent, of those animals in 

 which the gland was extirpated did not give 

 reliable results in the rate of growth as the 

 mouth was wholly or partially removed thus 

 interfering with feeding. For checks, unoper- 

 ated specimens and those in which the ablation 

 of the gland was unsuccessfully attempted were 

 available. The operated animals and checks 

 were kept in boiled water for five days and 

 then transferred to a frog tank where they were 

 in an essentially normal environment. 



The hypophysis-free animals grew more 

 slowly than the normal controls. No hypophy- 

 sectomized animals reached the size of the 

 largest checks and the averages of the two show 

 a noticeable difference. On June 6 the oper- 

 ated but not hypophysectomized animals had 

 an average length of 40—43 mm., the hypoph- 

 ysis-free animals averaging 33-35 mm. A 

 ratio such as this prevailed throughout their 

 growth. The ratio of body to tail length is the 

 same in the two classes, the difference in size 

 being uniform for all parts of the animal. 



Differences in color began to be noticeable 

 at an early stage. From then on the contrast 

 in pigmentation between the hypophysectom- 

 ized animals and the checks was striking. 

 Those animals without a hypophysis had a 

 slightly darkened silvery appearance of an al- 

 most uniform character; however, the dorsal 

 side was more pigmented than the ventral. 

 These are referred to as albinos. The checks 

 were a brown-black color often showing a 

 mottling. This color difference was more 

 noticeable over the body than on the tail, but 

 was evident in both regions and was the most 

 striking feature up to the time when the hind 

 legs began to appear in the checks. Sections 

 show that in the albinos the epidermis is pig- 

 ment-free while that of the checks is filled 

 with it. The subcutaneous pigment is present 

 in the albino in as great a quantity if not 



greater than in the normal animal. The ret- 

 inal pigment appears to be the same in both. 



The hind leg buds appear, normally, when 

 the tadpole has reached a length of 25-27 mm. 

 In the albino the hind limb buds appear but 

 slightly later than in the checks or when they 

 are from 26-28 mm. in length. From this 

 stage on, however, the hind limbs in the hy- 

 pophysectomized animals grow but little if at 

 all, although their total length increases at a 

 rate but slightly under the normal one. For 

 instance in 28 mm. checks the hind legs aver- 

 age 1.0 mm. ; in 30 mm. checks 2.0 mm. ; in 38 

 mm. checks 4.0 mm. In the albinos of each of 

 the above sizes and ages the hind legs were 

 0.1 mm. long. The above is in accord with 

 Adler ('14), 1 who found that the removal of 

 the hypophysis in a 20 mm. stage inhibited the 

 growth of the hind legs. 



Sections of the albino and normal animals 

 show striking contrasts in the organs. Of the 

 specimens yet sectioned none described above 

 as albino or hypophysectomized have had a 

 trace of the anterior lobe of the hypophysis 

 present. Thus it is certain that the entoderm 

 has not the intrinsic power to form a hypoph- 

 ysis, but that if it enters into the formation 

 of the gland at all it must be considered as a 

 tissue inclusion which may become changed 

 through its adaptability into glandular par- 

 enchyma, a conclusion previously drawn by 

 the writer Smith ('14) . 2 Comparison with 

 the checks shows that the infundibulum under- 

 goes structural modifications, although the 

 saccus vasculosus, as far as determined, ap- 

 pears to be normal. In the checks that region 

 of the diencephalon which rests against the pars 

 glandularis is of considerable thickness, hav- 

 ing in addition to the ependyma a rudimentary 

 pars nervosa. Caudad to this the wall is 

 formed almost entirely of ependyma. In the 

 hypophysectomized animals the pars nervosa 



1 Adler, L., ' ' Metamorphosestudien an Betra- 

 chierlarven. I. Extirpation endokriner Driisen. 

 A. Extirpation der Hypophyse, " Arch. f. Entwidk- 

 elungsmeeh. d. Organ., Bd. 39, 1914. 



2 Smith, P. E., ' ' The Development of the Hy- 

 pophysis of Amia calva," Anat. Bee, Vol. 8, 

 1914. 



