360 EXPERIMENTAL GIGANTISM 



lobe, however, commenced to grow so rapidly that their rate of 

 growth soon exceeded that which prevailed even during the earlier 

 period of life (see Fig. 3). At an age of 63 weeks, 26 weeks after 

 the beginning of the experiment, the smallest animal fed on anterior 

 lobe was 20 mm. larger than the largest control animal, although 

 at the beginning of the experiment it was 10 mm. smaller than the 

 smallest control specimen ; its weight was more than twice the weight 

 of that of the smallest control animal. At an age of 84 weeks the 

 largest animal of this series fed on anterior lobe measured 268 mm. 

 as compared with 197 mm., the latter being the size of the largest 

 control animal. Hence the size of the largest anterior lobe-fed animal 

 exceeds at present the size of the largest normal animal, on record in 

 the laboratory, by 68 mm. and the size of the largest specimen of the 

 eastern race of Amhy stoma tigrinum by 60 mm. It is 12 mm. smaller 

 than the largest specimen of the western race on record, which, how- 

 ever, cannot be considered normal, as pointed out above. Both the 

 controls and the anterior lobe-fed animals are still growing and at 

 the present time the rate of growth of the anterior lobe-fed specimens 

 is still higher than that of the control animals (see Fig. 3). It is pos- 

 sible, therefore, that in a short time, the largest anterior lobe-fed 

 animal will exceed in size even the largest western specimen known to 

 the writer. 



Experiment 3. — Six larvae (Series LV), of the same brood from which 

 the animals of Experiment 2 were taken, were raised on earthworms. 

 At the end of the second period of growth, about 19 weeks after 

 metamorphosis and at an age of 39 weeks, three of them (Nos. 1,2, 

 and 4), among them the largest one, were used as worm-fed controls; 

 the other three animals, among them the smallest one, were kept on 

 a pure anterior lobe diet (Table III) . The largest of these latter ani- 

 mals died soon after commencement of the experiment. 



The results were similar to those obtained in Experiment 2 and may 

 be seen from Table III and Fig. 4. At an age of 84 weeks the larger 

 one of the two hypophysis-fed animals measured 51 mm. more than 

 the largest control animal, and 44 mm. more than the largest animal 

 of the eastern race of the species known to the writer. The hypophy- 

 sis-fed specimens as well as the control animals are still growing, 

 but at present the growth of the anterior lobe-fed specimens of this 

 series is less vigorous than that of the controls. 



