474 Victor E. Ernmel 



each pail was placed a small paddle not unlike a boat propeller, 

 consisting of a vertical shaft with two horizontal blades at its 

 lower end. Each paddle was kept in motion by proper gearing 

 with a "live shaft." The blades were beveled so as to give an 

 upward movement to the current of water. In this way it was 

 possible to rear a small per cent of the mutilated lobsters through 

 the critical larval stages. 



After the fourth stage, the lobsters were placed in a floating 

 car divided into small compartments. Each lobster was kept in a 

 separate compartment and a careful record made of its mutilations, 

 moults and regenerations. 



EXPERIMENTS WITH LOBSTERS IN THE SECOND STAGE 



On July 24, 1906, two groups of lobsters were mutilated. 

 These lobsters had all hatched from the egg within about four 

 days. In Group A, the right chela, and in Group B, the left chela 

 was removed from each specimen. In spite of an exceedingly 

 great mortality, thirteen specimens were reared beyond the 

 sixth stage. After each moult the regenerated chela was inva- 

 riably removed. Thus the limb on the opposite side was given 

 a great advantage for growth in order to learn whether this chela 

 could be made to differentiate into a crusher. The results are 

 shown in the accompanying table. This table includes also the 

 data from a supplementary experiment made during the following 

 summer. In this experiment great difficulty was likewise experi- 

 enced in rearing the mutilated animals, for out of 200 larval 

 lobsters from which the right chela was removed, only three speci- 

 mens lived beyond the sixth stage. 



From the data for these sixteen lobsters it will be observed that 

 when the chelae had differentiated far enough to display asymme- 

 trical characters, the claws which regenerated after amputation 

 were all nippers; at the same time, the claws which were not 

 mutilated, being thus given the greater advantage in growth, were 

 all crushers. 



