August i, 1916] 



SCIENCE 



179 



reverse by stimulation with pieces or the juices 

 of crab meat, these ciliary tracts thus consti- 

 tuting a mechanism through which the feed- 

 ing process can be controlled. 



In this paper Parker refers also to a num- 

 ber of papers, not easily available to the writer 

 and not referred to by Dr. Kellogg, in which 

 the reversal of ciliary movement in metazoans 

 has been observed. Of special interest in this 

 connection are those by Engelmann and others 

 in which the reversal of cilia of the palps of 

 lamellibranchs is described. 



The only positive evidence I can offer for the 

 conclusion that the oyster is able to select food 

 is that afforded by a microscopic examination 

 of its stomach contents. The various species 

 of diatoms there found are not present in the 

 same relative proportions as they exist in speci- 

 mens of water collected in the vicinity of the 

 bed from which the oyster fed. Furthermore, 

 certain species of diatom (for example, Rhizo- 

 solenia), abundant in salt water, are seldom 

 found in the alimentary tract of the oyster. 

 The absence of these diatoms from the alimen- 

 tary canal can hardly be due to their spiny 

 structure because their size is not sufficiently 

 great to prevent their being carried by ciliary 

 currents or entering the mouth. 



The observations that have been made of the 

 reversal of the beat of cilia in both protozoa 

 and metazoa, and of the ability of various ani- 

 mals to so control the movement of the cilia 

 as to accept or reject food particles presented 

 to them, at least suggest the possibility that 

 the oyster may also have some power of food 

 selection and that reversal of the cilia of cer- 

 tain tracts on the palps, resulting perhaps 

 from their stimulation directly or indirectly 

 by food particles, may be the mechanism by 

 which the selection is effected. 



Why, then, if a reversal of cilia and selec- 

 tion of food takes place in lamellibranchs, did 

 so good an observer as Dr. Kellogg fail to see 

 the reversal process? To me it seems clear 

 that it was due to the fact that the animals on 

 which he made his observations were, in every 

 case, in a mutilated condition. In the case of 

 his experiments on the oysters the shell was 

 first removed and in its removal the adductor 



muscle was cut and the visceral ganglion, 

 which is embedded in this muscle, was neces- 

 sarily severely injured. Under such a condi- 

 tion of shock normal behavior is not to be 

 expected, especially in the case of activities 

 that may be subject to nervous control. The 

 history of the animals experimented upon by 

 Dr. Kellogg, whether they were in a state of 

 hunger or satiety, was also unknown. 



EXPERIMENTS 



During the years 1909 and 1910 oysters 

 planted on beds located in Buzzards Bay re- 

 mained poor and the death rate among them 

 was unusually large. Coincident with and fol- 

 lowing the same period, dredging operations 

 were carried on in the vicinity of certain of 

 these oyster beds which caused an unusual 

 amount of sediment to be carried from the 

 dredges across the oyster beds with the rising 

 tides. 



The oyster planters readily imagined that 

 the poor condition and death of their oysters 

 were in some way causally connected with this 

 sediment in the water and they brought suit to 

 recover their losses, with generous interest, 

 from those responsible for the dredging opera- 

 tions. 



During this litigation it has been the oral 

 contention of Dr. Kellogg that, since the 

 oysters planted on the beds located near the 

 operating dredges were exposed on rising tides 

 to unusually turbid water and since food-bear- 

 ing sediment was therefore entering the mantle 

 cavity of the oysters during these intervals in 

 unusual abundance, the oysters were underfed 

 and starved because the ciliated food-collecting 

 mechanism of the palps must, under such con- 

 ditions, transport the food-bearing material 

 away from instead of to the mouth. 



The ciliated food-collecting mechanism of the 

 oyster is so constructed, according to the theory 

 held by Dr. Kellogg, that it can transport food 

 material to the mouth only when the food par- 

 ticles reach the ciliated tracts few at a time, 

 for when they reach the palps more rapidly 

 they are seized automatically by the cilia of 

 outgoing tracts. It is an important part of his 

 theory that the direction of the beat of the 

 cilia composing the food-transporting mechan- 



