448 Charles R. Stockard 



The influences of regeneration seem to be opposite in the two 

 cases studied by Zeleny and Emmel. In the adult crayfish Zeleny 

 finds that the time elapsing between molts is less in those individ- 

 uals regenerating most tissue and Emmel finds the reverse true 

 in the larval lobsters. In a short review of these papers^ I at- 

 tempted an explanation of this contradiction as follows. The 

 larval lobsters are growing at their maximum rate and by neces- 

 sitating further growth through the removal of limbs the entire 

 growth rate is lowered as Emmel's results show to be the case, and 

 this slower growth of the regenerating specimens brings them more 

 gradually to the condition necessary for the following ecdysis. 

 The adult crayfish, on the other hand, is living and growing at a 

 rate below its possible maximum, it may be said to have a reserve 

 growth energy. The introduction of regenerative processes such 

 as the removal and subsequent regeneration of limbs calls out this 

 reserve (recuperative power) and the rate of growth rises above 

 the normal. The time elapsing between successive molts is thus 

 decreased. This difference in states between the almost stable 

 adult body and the rapidly increasing larva must always be borne 

 in mind when comparing animals in different periods of life. 



Finally, there is another cause of error to be guarded against 

 in calculating the specific amounts of regeneration in animals 

 injured to different degrees. This calculation according to the 

 method employed by Zeleny is made by dividing the length of new 

 tissue by the body length of the individual at the time of measur- 

 ing the new tissue. I find that in some animals injured to differ- 

 ent extents, or regenerating different amounts, the body size de- 

 creases during the experiment more in those more injured than in 

 others less injured, so that in order to get proper comparisons the 

 original body length must be used in the calculations. For in- 

 stance, the medusae which are to be considered below decrease 

 in body size much more rapidly when six or eight oral-arms have 

 been removed than when fewer are cut away, and at the same time 

 may actually regenerate the individual arms faster. The length 

 of new tissue divided by the body length (disk diameter) would 



' The Influence of Regeneration on Molting in Crustacea. Am. Naturalist, XLII. 1908. 



