852 



SCIENCE 



[N. S. Vol. XLIV. No. 1146 



DISCUSSION AND CORRESPONDENCE 



OPINIONS ON SOME CILIARY ACTIVITIES 



In Science for August 4, 1916, Professor C. 

 Grave has questioned the accuracy of some of 

 my conclusions concerning the ciliary mech- 

 anisms of lamellibranchs, dealing with the 

 ingestion of food, that were published in the 

 Journal of Morphology, Vol. 26, No. 4. 



Those statements of mine which he has diffi- 

 culty in accepting are: 



1. Volume alone determines whether the 

 collected foreign matter that reaches the palps 

 shall proceed to the mouth or shall be sent 

 from the body on outgoing tracts of cilia. 



2. A lamellibranch is able to feed only when 

 waters are comparatively clear — when diatoms 

 are brought to the gill surfaces a few at a 

 time. In muddy waters all suspended par- 

 ticles, of whatever nature, are led to outgoing 

 tracts. 



3. There is no selection or separation of 

 food organisms from other water-borne par- 

 ticles. 



4. The direction of the beat of cilia is never 

 changed. 



The only facts bearing on these statements, 

 that are offered from Professor Grave's own 

 experience, are those derived from an oyster- 

 feeding experiment made at Buzzards Bay, and 

 these bear only on the second statement, 

 namely, that lamellibranchs feed only when 

 waters are comparatively free from suspended 

 particles. 



Professor Grave has referred fully enough 

 for the purpose, to the litigation that led to his 

 experiment. Planted oysters had died in great 

 numbers at the mouth of the Monument River 

 after dredging operations were begun in the 

 oyster field, and below it in Buzzards Bay. He 

 wished to show that oysters could live in the 

 turbid water. Taking individuals gathered 

 at a distance, he deprived them of food for 

 three days, then at a certain point immersed 

 them " in the turbid water " for periods of one, 

 two and three hours, at the end of which pe- 

 riods their stomachs contained from 2,850 to 

 18,500 food particles. In some cases, also, 

 there was so much sediment that a diatom 

 count was not possible. Some oysters were 

 allowed to remain on the bottom for two 



weeks, and "all thrived and made perceptible 

 growth of shell." 



My contention, based on thousands of ex- 

 aminations of the operation of the palps in 

 very many species of lamellibranchs, and ex- 

 tending through many years, was that when 

 solid particles in sufficient volume are brought 

 to the apposed palp surfaces, they overflow the 

 narrow tracts leading to the mouth from either 

 side, so as to touch outgoing tracts that border 

 them, and by these are carried away and even- 

 tually removed from the body. My assumption 

 was that, in this particular case, waters had, 

 during long intervals, been so laden with fine 

 sand and bast fibers from decaying vegetable 

 matter, liberated by the dredging operations, 

 that oysters over the field in general had been, 

 through the action of the ciliary mechanisms 

 of the palps, so often deprived of nourishment 

 that they were gradually weakened and finally 

 destroyed. They were not killed at once, for 

 during a part of the ebb tide relatively clear 

 water coming down from flats above the bay 

 presented conditions favorable for feeding. 

 Some had remained alive for more than two 

 years under the adverse conditions. Here and 

 there even the young had grown for a time. 

 The condition of the field in 1911 indicated, 

 and the owners of the beds testified, that, in 

 general, there had been a gradual elimination. 



The results of Professor Grave's feeding ex- 

 periment seems to him to " show conclusively 

 that oysters can and did feed actively in waters 

 that were turbid with sediment, a fact that is 

 in direct opposition to Dr. Kellogg's conclu- 

 sion numbered (2) in this paper [and in the 

 present one], and one that casts doubt upon 

 the correctness of the three other conclusions 

 herein discussed." 



During a period of two weeks, Professor 

 Grave's oysters " thrived and made perceptible 

 growth of shell." This is not a very full or 

 definite statement of his net results in the 

 matter of growth, but it is all that he has 

 given. At the same time, it was the testimony 

 of all the oyster planters, as well as my own, 

 after I had examined their beds, that, far from 

 thriving, a large proportion of their planted 

 oysters had died, after several months — so 



