328 MORGAN. 



The change in shape of the piece, i.e., the production of the 

 typical form, is primarily the result of a shifting of the material 

 that carries with it a loss of material in the old part. Other 

 so-called formative factors may have some share in the reduc- 

 tion in size of the old peristome to one proportionate to the 

 rest of the piece, but the simple loss of material will, I think, 

 account for the greater part of the change. 



What primarily brings about this change in the material so 

 that the typical form is produced is a question to which at 

 present there is no answer. 



BRYN MAWR, March 12, 1901. 



