246 Papers from the Department of Marine Biology. 



RESPONSE OF INJURED CELLS. 



If a number of noctilucas are punctured with a needle, causing the 

 cells to collapse, and are then subjected to an interrupted current, they 

 respond just as uninjured cells do. Such punctured and collapsed cells 

 likewise give a normal response when stimulated mechanically — i. e., 

 by pressure of a cover-slip. 



Noctilucas are injured by a few shocks of the strong induced current; 

 the protoplasm shrinks away from the cell-wall, leaving a clear area at 

 the periphery. If the animal is further subjected to an induced cur- 

 rent, there is again a response, the protoplasmic area becoming lumi- 

 nous, while the clear peripheral area does not. After a short time the 

 cell collapses and the animal appears as a shrunken mass of protoplasm 

 within an irregular membrane. These shrunken anunals also respond 

 at the break of a weak induced current with a flash, just as normal 

 cells do ; and they likewise give a normal response to mechanical stim- 

 ulation — i. e., if pressed by a needle. It is thus shown that injury to a 

 noctiluca does not interfere with its response to mechanical or elec- 

 trical stimulation. 



If, however, the injury to the cells is too great, and the cells are 

 completely broken to pieces, they do not respond to stimulation. By 

 pressing a mass of noctilucas through cheese-cloth, a filtrate was ob- 

 tained containing many empty membranes and fragments of cells, 

 visible under the microscope. This filtrate, although luminous, did 

 not respond to electrical stimulation. Another filtrate obtained by 

 pressing a mass of noctilucas through fine-meshed bolting-cloth, and 

 tested while still luminous, did not respond to electrical stimulation. 

 It is possible, however, that the fact that the noctiluca juice is acid 

 may have some effect on the response in these cases. 



LOCATION OF LUMINOUS MATERIAL. 



When a noctiluca is giving a bright, constant glow — for instance, 

 when treated with n/2000 to n/4000 HCl^t is fairly easy to observe 

 the light under a microscope in a dark room. The chief luminescence 

 comes from the main mass of protoplasm near the mouth-groove and 

 around the periphery of the cell, while the area between these two 

 regions is much fainter. The luminescence is a general glow over the 

 cell, and a similar glow is suffused momentarily over the cell when a 

 noctiluca is stimulated by a needle. This effect is, however, probably 

 due to a close aggregation of small luminous particles, for when noc- 

 tilucas are crushed under the microscope and the particles separated 

 by means of a cover-slip, numerous points of light may be observed, 

 similar to stars in the sky. The luminescence, therefore, apparently 

 comes from small granules in the protoplasm, which may be freed from 

 the cell by crushing. That the luminous granules are located in the 

 protoplasm and not elsewhere was shown by stimulating cells injured 



