No. 399.] - NOTES ON PLANARIANS. 177 
undergoing a translocation and partial redifferentiation to 
accommodate themselves to the new proportion that must be 
assumed. The new tissue at the cut end must be formed 
entirely from the old tissue, and the final result involves, there- - 
fore, an extensive working over of the old material. The 
original tissues, with constant losses, owing to destructive 
metabolism, are moulded into the form of a new individual. 
In trying to form a mental image of the forces at work in this 
complex rearrangement, one can think only of an “internal 
mould" (an expression of Buffon to which Professor Whitman 
has called my attention) No less remarkable is the mainte- 
nance of form in individuals that gradually waste away to one- 
hundredth part or less of their original bulk. Such individuals 
in all stages of reduction appear normal in all respects, physi- 
ologically as well as morphologically. They are active and 
exhibit perfectly normal reactions, showing no indications of 
sickness. 
VASSAR COLLEGE, Jan. 4, 1900. 
