REPORT OF COMMISSIONERS OF INLAND FISHERIES. 173 



when absent from the skeleton generally as is the case in these larval 

 lobsters. We found that the older fourth-stage lobsters, and also 

 fifth-stage and older lobsters, have gastroliths. This observation is 

 suggestive because it shows that the gastroliths appear in conjunc- 

 tion with the limy skeleton, since the fourth is the first stage in which 

 the lobster has a calcareous skeleton. So far as we know, the gas- 

 troliths have not been found before in lobsters smaller than 7| 

 inches. 



We determined to discover, if possible, the time of appearance, the 

 rate of growth, and the rapidity of solution of the gastroliths in 

 fourth and early fifth-stage lobsters. At the beginning of our 

 observations for this purpose we had about 500 fourth-stage lobsters 

 which molted from the third stage on the night of August 7 and 8. 



Mr. Emmel, who obtained these lobsters for experiments on 

 regeneration, and to whom we are indebted for the opportunity to 

 perform this collateral experiment, isolated a number of these in 

 ■bottles and fed them daily as controls. After removing a number of 

 others for mutilation, the remaining lobsters were kept in a large 

 receptacle and fed daily. The controls began to molt on the eighth 

 day, but the molting of the reserve supply was delayed until the 

 eleventh or twelfth day. 



We examined the stomachs of several lobsters each day, and found 

 that the gastroliths appeared on the fourth day — that is, the gas- 

 troliths begin to be formed in the middle, or at the beginning of the 

 middle third, of the eight to twelve day period. 



At the periphery of the ovately-triangular area, which is finally 

 covered to a considerable thickness by the gastrolith, the calcifi- 

 cation begins with the formation of irregular discs which are thick 

 at the edge and thinner toward the center of the gastrolith where at 

 first each disc is undefined, but later has a definite edge which, for 

 a long time, is markedly thinner than the outer edge. The calci- 

 fication proceeds by the thickening of tlie peripheral discs, by the 

 addition of central discs, and by the gradual expansion of all tlie 



