Crttslaceaiis. 



47 



VI. 



CRUSTACEANS. 



VERY radical and far-reaching is the reproduc- 

 tive change which takes place during the 

 breeding season. Even in the 

 higher life great parental sac- 

 rifice is involved, and the 

 whole body undergoes pro- 

 found modifications under the 

 sway of the reproductive 

 force. During the breeding 

 season life speeds along as 

 it were under high pressure, 

 the vital activity prodigious 

 ly increased in certain parts 

 of the organism, and cor- 

 respondingly decreased in 

 others. It is a law of life 

 that excessive activity of one 

 system is accompanied by decreased or suspended 

 activity of others. 



So, for instance, when the reproductive activity 

 is at its height the digestive and assimilative activ- 

 ities are partly or wholly suspended; this may be 



