148 Pub. Puget Sound Biol. Sta. Vol. 2, No. 43 



Table 6. Sporelings 48 hours old, then grown for 5 weeks on 

 shells suspended in the sea at different depths 



seemed to be alive^ and a later examination showed clearly that it was 

 alive and growing. The other three were completely covered with diatoms. 

 Another cord contained seven healthy sporeling 3 dm. from the surface of 

 the water. Two shells on the same cord, one 6 dm. and the other 1 m. 

 below the surface of the water, still retained two sporelings each. How- 

 ever, they had but little color and were thought to be dead. The other 

 shells on the cord had no sporelings remaining on them. A third cord 

 showed 13 healthy sporelings 3 dm. below the surface of the water^, and 

 each showed a protuberance on one side. One shell 5 m. below the sur- 

 face of the water contained what was believed to be a sporeling. It was 

 surrounded by diatoms, was very light colored, and the cells appeared to 

 be breaking down. The fourth cord was lost in the Sound before any 

 data was gathered. 



The changes from the natural habitat were continual submergence, 

 light and diatoms. If it were the effect of being continually submerged 

 that produced death among the sporelings, all would have died, since they 

 were all submerged alike. If it were caused by diatoms, one would expect 

 those above low tide to be about equally affected, as is the case with 

 Cladophora. 



No living sporelings were found over 3 dm. below the surface of the 

 Avater. A few sporelings were still held to the shells. In these, how- 

 ever, the growth which had taken place occurred during the first 2 weeks, 

 and they were now considered dead. 



Light in the water diminishes as the depth increases. The living 

 sporelings were found at 3 dm. below the surface of the water. Shells 

 submerged between 3 dm. and 6 m. still had occasional dead sporelings 

 clinging to them. Below this no sporelings were found. The number of 

 sporelings also decreases with the distance below the surface of the water, 

 or the number of sporelings became less as the light decreased. Thus 

 light seems to be a controlling factor. The shells below 6 m. contained 

 no sporelings and no diatoms. The shells that contained living sporelings 



