Compensatory Regulation. 3 



of a species, notwithstanding environmental changes within a 

 fairly wide hmit. At the same time members of different species 

 are constantly dissimilar notwithstanding similar external environ- 

 ments in many cases. 



Disturbances of the system of an organism as above conceived 

 may be conveniently grouped under two heads: First, disturbances 

 in external environment, not considered here, and second, direct 

 internal disturbances. As direct internal disturbances may be 

 classed all mutilations. The removal ot a part causes disturb- 

 ances in the remaining parts which as the result of a new mode of 

 interaction adjust themselves to a new stable system. As an 

 example may be mentioned the rearrangement of the leaflets of a 

 compound palmate leaf after removal of one of them. When 

 complete regeneration takes place the new system may finally 

 regain its original condition. However, during the intermediate 

 stages while the regeneration of the organ is in progress a new 

 condition of interaction must be present and this may lead to 

 changes both in the old parts and in the new regenerating 

 ones, so that the new stable equilibrium is very different from 

 the old. 



In a paper on the dimensional relations of the members of com- 

 pound leaves, the writer has described the changes taking place in 

 the members of a compound leaf after removal of one of the leaf- 

 lets at an early stage. In this case there was no regeneration and 

 the effects of the operation were confined to position and length 

 changes m the remainmg members. The results of these experi- 

 ments will be considered briefly in a separate section at the begin- 

 ning of the following discussion. 



The present paper will deal, except for the above mentioned 

 experiments, with cases among animals where, as a result of the 

 operation, the character of regeneration of an organ varies with 

 the character of the remainder of the system as in the arms of 

 Ophioglypha and the opercula of Apomatus, or where there is an 

 evident change not only in the regenerating part but also in other 

 parts of the system, so that the final state of equilibrium differs 

 from the original condition, as in the opercula of Serpulids and 

 the chelae of Alpheus. The experiments on Ophioglypha have 

 already been described in a preliminary paper (Zeleny, '03a), 

 and likewise some of the experiments on the Serpulid, Hydroides 

 dianthus (Zeleny, '02). 



