FEEDING THYMUS TO FROG LARVAE. 



125 



OBSERVATIONS OF MAY 20. 



Examination of the larvae at this date revealed no difference 

 between the animals of the control and thymus-fed groups as 

 regards pigmentation, body shape, size or activity. The limb 

 buds of both groups had by this time differentiated into their 

 two primary divisions, and had well developed toe points. The 

 size of the limbs of both groups appeared to be the same. The 

 dark pigmentation of the thymus-fed larvae had gradually faded 

 out, and was no longer visible on May 20. Table VII shows 

 the average lengths of the animals of the experimental and control 

 groups. The average length is nearly the same in all groups. 

 The greatest difference in length between the thymus-fed and 

 control larvae was about two millimeters. 



TABLE VII. 



MAY 20. 

 Length. 



All larvae which had developed the two primary divisions of 

 the legs in this series, had well-developed toe points. 



The larvae were not measured again until June 8, eighteen 

 days from the date of previous measurement. The larvae had 



