370 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



F. P. The rule seems to be that F. P. is wholly arrested 

 until the ^art cut away, i, e., ^. _^., is entirely restored 

 by regeneration. This regeneration having been accom- 

 plished, F. P. then proceeds to completion. This we say- 

 seems to be the rule. We have not yet sufficient data on 

 the point to put the conclusion wholly beyond question; 

 there is little doubt, however, that further observations will 

 do so. 



6. A Few Theoretical Considerations. 



(a) Comparison of the Diversion of a. f. -p. from Its 

 Original Destination, with the Diversion of Elastomer es in the 

 Embryo. — The "regulation" here accomplished may be 

 compared with that wherein some of the blastomeres of the 

 segmenting ^^,^, as in the familiar experiments of Driesch, 

 Wilson, and others, are diverted artificially from their natural 

 course and induced to take some other part in the formation 

 of the adult animal than that for which they were originally 

 destined. Various obvious and important differences be- 

 tween the two are, however, to be observed: The diversion 

 is much wider in the case of Stenostoma; i. e., while the 

 blastomeres of the embryo are made to produce some part 

 of the animal other than that which they would have pro- 

 duced in normal development, in Stenostoma the piece 

 (a. f. -p.) which would be compared with the diverted 

 blastomere or group of blastomeres is not only diverted to 

 the production of a part of the organism other than that for 

 which it was originally destined, but is diverted from one 

 individual animal to another ; i. e., what would have become 

 the tail end of one animal is induced to become the head of 

 another. Nor can the transfer of this piece from one indi- 

 vidual to another be compared strictly with grafting, for, in 

 the first place, the really successful graft is both physiolog- 

 ically and morphologically similar to, if not actually homol- 

 ogous with, the part which it replaces; and in the 

 second place the scion ordinarily retains its original char- 

 acters. We do not forget, in connection with the first 



