196 ORIGIN OP NON-SEXUAL CHARACTERS 



and the rest dying, lying at the bottom motionless. 

 They now had the tail much shorter, and the fore-legs 

 showing as well as the hind, but the latter not very 

 long, and without joints or toes. 



Period from first feeding with thyroid, thirty days. 

 I now decided to feed the controls with thyroid, 

 expecting that as they were large and vigorous they 

 would have strength enough to complete the meta- 

 morphosis and become frogs. 



May 15. Fed the controls with thyroid for first 

 time. 



The smallest of them was in total length 1-7 cm. 



body, 0-7 

 tail, 1-0 



The largest measured was in total length 2-2 



body, 0-8 

 tail, 1*4 



May 25. All but two of the tadpoles dead. The 

 tails were only half the original length, all had well- 

 developed hind-legs, some with toes, but the fore-legs 

 were beneath the opercula, not projecting from the 

 surface. 



Smallest total length, 1-2 cm. 

 body, 0-5 

 taU, 0-7 



Largest total length, 1-8 



body, 0-7 



tail, 1-1 



These last measurements were made after the 

 tadpoles had been preserved in spirit, and were 

 therefore doubtless somewhat less than in the fresh 

 condition. Making allowance for this it is evident 

 that the tails had undergone reduction as part of the 



