EDUARD UHLENHUTH 351 



two different females. Many animals of this species were observed 

 for a period of over 2 years and behaved essentially the same way. 

 Fig. 1 shows the growth curves of the four v3 year old animals and illus- 

 trates the most important characteristics of the growth of that species. 

 Although each animal, during the larval period, was treated in a dif- 

 ferent way (Di normal, E3 underfed, Wca5 kept in water -\- a small 

 amount of Ca lactate, WNa4 kept in water + a small amount of 

 Na lactate) all four curves are about the same. The most rapid 

 growth takes place during the larval period (first period of growth) ; 

 at the end of this period a decrease in size is noticeable which may last 

 for several weeks and corresponds to metamorphosis. The second 

 period of growth lasts from after metamorphosis till the first breeding 

 season, at which the animals are about 1 year old. The beginning of 

 the breeding season in the male may be recognized by the swelling 

 and reddening of the cloacal region and in both males and females by 

 the cessation of food intake. During the second period of growth the 

 animals continue to grow at a fairly high rate; during the first as well 

 as the following breeding seasons little growth or even a decrease in 

 size may be noticed. The third period of growth begins after the 

 first breeding season and lasts till the third breeding season, and is 

 characterized by slow growth. No records are available to deter- 

 mine the behavior after the third breeding season, but to conclude 

 from the normal maximum size of the species growth seems to be 

 nearly completed at the end of the third period. The control animals 

 of the hypophysis-fed series exhibit a similar type of growth (Fig. 2) , 

 although they were from a different season (1918) . It is safe to assume 

 that this is the type of growth characteristic for the species Amhy stoma 

 opacum. The most important feature of it, in connection with the 

 following experiments, is the considerable slowing down of growth 

 after the first breeding season. 



As to the normal size of the species, the following records are avail- 

 able. The largest animal on record in my laboratory was 115 mm. 

 long at an age of 79 weeks (it was one of the controls of the hypophy- 

 sis-fed animals). The largest animal among fifteen specimens of 

 from 2 to 3 years of age, still alive at present, measures 113.5 mm., 

 the average size of these fifteen animals being 103.5 mm. (the small 

 size of some of them may be due to the abnormal conditions under 



