II. SIZE OF THE BODY AND ORGANS 



89 



captivity, gave thyroid weights as entered in reference table 

 148. Since then, however, the weight of the thyroid in these 

 domesticated Albinos has shown a marked diminution and 

 to-day (at the body lengths of the captive Grays) is only 

 some 48 per cent (male) and 47 per cent (female) of its origi- 

 nal table value. Here, then, is a marked change in the thyroid 

 weight of the Albino occurring after many generations in cap- 

 tivity. This must be due to some special condition, and it 

 seems most probable that some change in the food or its 

 method of preparation has acted as the cause. 



It appears, therefore, that the weight of the thyroid under- 

 goes a progressive decrease in the captive Grays, probably in 

 response to some special food conditions. There is a sag in 

 the graphs at G c and G 7 . The final weight values at GI O drop 

 below those for the Albino as given by our current records, 

 while the weight relations according to sex become those for 

 the albino strain (i.e., on body length the female thyroid is 

 heavier). 



In this connection we enter some observations by Miss 

 Meeser on structural deficiencies observed in the thyroid and 



TABLE 19 



Thyroid weights in the captive Grays and deviations from the corresponding 



standards on body weight and body length. (Chart 19.) 



Albino standard. Males 



