6 Papers from the Marine Biological Laboratory at Tortugas. 



system, while they are initial depressants for ciliary movement, but 

 after a brief interval of cessation the movements of the cilia recover and 

 become quite active. 



It is probable that, in common with neuro-muscular movements, 

 ciliary movement is not normally caused by stimuli originating from 

 the outside, but is controlled by internal stimuli which in primitive cilia, 

 such as those of ordinary epithelial surfaces, arise within each ciliated 

 cell itself, and is only weakly under the control of the nervous or muscular 

 system of the animal. Such ciliated cells ma\^ be separated one by one 

 from the epithelium and each isolated cell still continues to lash its 

 cilium in a normal manner. At best only a weak coordination exists 

 between the constituent cells of such an epithelium, and impulses are 

 only slowly transmitted by deep-seated cells lying under the cilia in the 

 manner shown by Kraft, 1890, Archiv fur gesammte Physiologic, Bd. 47, 

 p. 196, or Gruetzner, 1882, Zur Physiologic des Flimmerepithels; Physiol. 

 Studien, p. 1-32. 



On the other hand, the more highly differentiated cilia, such as those 

 of the combs of Ctenophores, which move in a coordinated rhythm, are 

 certainly under the control of the nervous or muscular system of the 

 animal. When this control is destroyed by placing the animal in mag- 

 nesium chloride the cilia beat independently and incessantly and lose all 

 coordination; thus reverting to the condition of the cilia of ordinary 

 epithelia. It is therefore probable that for ciliary movement the com- 

 bined stimulating effects of the magnesium, calcium, and potassium of 

 the sea-water counterbalance the inhibiting effect of the sodium, for we 

 find that in trochophores of marine annelids the cilia move with more 

 than normal activity when the animals are placed in a solution lacking 

 sodium but containing the proportions and amounts of magnesium, 

 calcium, and potassium found in sea- water. 



If, on the other hand, they be placed in a pure sodium solution, their 

 cilia immediately decline and soon cease to beat and are so injured that 

 recovery does not occur. 



In experimenting upon the effects of the cations sodium, magnesium, 

 calcium, and potassium upon unicellular motile fungi and algae I find 

 such great diversity in their reactions that one can not find any general 

 law, this being in marked contrast to the uniform behavior of animals 

 from the protozoa to the vertebrates. There is, however, an actively 

 moving transparent Spirillum which lives in a culture of dead house- 

 flies in fresh water containing algae. This form reacts to the ions Na, 

 Mg, Ca, and K as do the cilia of animals. It is therefore possible that 

 the ciliary movements of animals were taken directly from their plant-like 

 ancestors, while their muscular movements were developed only later and 

 in a mode the exact converse of ciliary movement. This hypothesis must, 

 however, be taken with the greatest reservation, and I present it only as 

 a mere speculation calling for further study. 



Hargitt, 1899 (Biological Bulletin, vol. i, p. 42), succeeded in causing 

 two individuals of Gonionenius to unite by their bell-rims, and whenever 

 one of the individuals pulsated the other moved in coordination. The 

 medusae being joined rim to rim, it would seem, however, that if one 



