CHAPTER XXI 



DEVELOPMENT 



Thremmatology is interested in growth as well as in reproduc- 

 tion ; in the proper development of valuable characters as well 

 as in their transmission and inheritance. 



What an individual comes to be at maturity is a kind of result- 

 ant of the characters born into him and the opportunities for 

 their development afforded by the conditions of life. While the 

 surroundings during development cannot in any sense compen- 

 sate for deficiency in inheritance, the opposite is also true, that 

 the richest heritage is fruitless of results if conditions of life 

 make their development impossible. 



External conditions only indirectly causes of variation. Con- 

 ditions external to the organism thus operate only indirectly as 

 causes of variation. Their good results depend entirely upon the 

 capacity on the part of the individual or the breed to avail itself 

 of their advantages, and this capacity is born into the organism 

 or it does not possess it, it cannot be implanted from without. 

 That is to say, no amount of feeding would make draft horses 

 out of those that are racing bred, or beef cattle out of those 

 bred for the dairy, and it would be a great waste of feed to try 

 it. Certain experiments with individual animals, it is true, seem 

 to teach that Jerseys, for example, are successful feeders. Such 

 experiments will deceive no one who realizes the full extent of 

 variability in all breeds, and that individuals can be found to 

 prove almost anything. When some adventurous investigator will 

 take the trouble to feed off three hundred Jerseys against three 

 hundred Shorthorns, and work out the mean and the standard 

 deviation for both, then he will learn that a breed cannot be 

 selected for unknown generations for milk only, and still retain 

 or attain meat-producing powers equal to those of a breed 

 selected almost exclusively for that purpose. If it could, there 

 is little in selection and less in breeding, and the wonder is that 



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