REGENERATION IN CAMBARUS. 307 



Miss Steele's experiments on C. virilis and gracilis were carried 

 on for a sufficient length of time, but she found it difficult to pro- 

 vide the sanitary conditions necessary to such prolonged experi- 

 mentation. The specimens used in her work were probably too 

 old to give the best results. They measured not more than three 

 inches in length, a size which would indicate that they were 

 several years old at least. The younger the specimens used, the 

 more frequently the moults take place. Those used in my ex- 

 periments measured from one and six tenths to two and five 

 tenths cm. in length, and were probably at the beginning of the 

 second or third year. Two individuals measuring five cm. in 

 length were also used. These did not yield as satisfactory 

 results although some regeneration occurred. The difference 

 was probably more in the frequency of moulting than in any- 

 thing else. While one moult took place in these older ones, I 

 could secure three in the younger. And to have kept the older 

 individuals until the same number of moults occurred as in the 

 younger ones, would have required two years instead of four or 

 five months. The use of more nearly adult material, and the 

 fact that slight attention was paid to the swimmerets may account 

 for the slight regenerative power which Miss Steele was able to 

 report. 



My experiments show that the swimmerets of young specimens 

 of C. (Bartonius] bartoni regenerate rapidly, and that the regen- 

 eration of any of the appendages may be practically completed 

 in a single season of growth. The regeneration is not particularly 

 slow in beginning, having become visible in one instance only six 

 days after the operation was performed. It is usual, however, to 

 find that the regeneration begins and takes place under the old 

 exoskeleton, without showing any visible indications that the new 

 parts are forming. For instance, No. 9 moulted on March 28, 

 four days after the operation, and no regeneration could be noticed. 

 The next moult took place April 30, but during that time no in- 

 dication whatever that regeneration was occurring could be seen. 

 Nevertheless, when the moult occurred it was evident that regen- 

 eration had taken place. If the experiment had been continued for 

 only thirty days, the conclusion naturally drawn would have been 

 that regeneration either did not occur, or was " very slow in begin- 



