REPORT OF COMMISSIONERS OF INLAND FISHERIES. 59 



effect of close planting or overcrowding on the rate of growth? We 

 are, as yet, not prepared to give a final answer, for the evidence from 

 different observations has been more or less contradictory. The 

 clams planted in the sand boxes at the houseboat, described under 

 experiment No. 2, grew very rapidly, though they were so close to- 

 gether that their shells almost touched. On the other hand, the 

 following experiment showed a very distinct dwarfing effect from 

 overcrowding. 



In September, 1902, a pint and a half of very small clams which 

 remained over from another experiment were poured upon the 

 ground and covered with a circular sieve to keep them from be- 

 coming scattered. The clams were spread as evenly as possible, 

 but were so thick' that they touched one another, and in some places 

 were piled two or three deep. Just beside this place other clams of 

 the same size were planted about two inches apart and covered with 

 wire screening. The next day all of the clams, with the exception of a 

 few crushed ones, had burrowed, and, after the sieve was taken up, 

 the circular area was plainly defined by the abundance of clam holes. 

 The clams were, from this time, protected by wire screening and left 

 undisturbed for about one year. When the netting was removed 

 and the place examined again, in October, 1903, the outline of the 

 original area of thickly planted clams could still be traced readily, on 

 account of the munerous holes, although it had become somewhat 

 uneven. The clams were small and stubby, and the shells were 

 thick and deeply scarred. Although they were now about a year and 

 four months old, they were not as large as the average clams of six 

 months. 



The control specimens, which were planted near them and given 

 plenty of room, showed at this time a good average growth. In 

 Fig. 14 are shown samples of both kinds. 



Experiment No. 8. In this experiment we made use of the device 

 mentioned on page 54, of recording the growth by notching the shell. 

 Clams w^ere selected from various localities of different sizes and 

 ages. After each specimen was carefully notched, they were all 



