Vol. XLVII. November, 1924. No. 5. 



BIOLOGICAL BULLETIN 



REACTIONS OF THE LARV.E OF THE SHRIMP, 



PALMMONETES VULGARIS, AND THE 



SQUID, LOLIGO PEA LI I, TO 



MONOCHROMATIC LIGHT. 



GERTRUDE MAREAN WHITE, 



MARGARET MORRISON CARNEGIE COLLEGE, CARNEGIE INSTITUTE 



OF TECHNOLOGY. 



Since the larvae of the shrimp, Palcemonetes vulgaris, and the 

 squid, Loligo pealii, react to light very positively, it seemed 

 interesting to discover what portion of the spectrum is most 

 effective in stimulating them. For this purpose experiments 

 were performed at the laboratory of the U. S. Fish Commission 

 during the summers of 1920 and 1921 and at the Marine Biological 

 Laboratory, Woods Hole, Mass., in the summer of 1923. The 

 w r riter is indebted to Dr. S. O. Mast for valuable suggestions and 

 criticism. 



METHOD. 



It was found that when the larvae of the shrimp, Palcemonetes 

 vulgaris, and the squid, Loligo pealii, are exposed to light, they 

 turn and move definitely in the direction of its source. When 

 exposed in a square aquarium at the intersection of two beams 

 of light of equal intensity and at right angles to each other, the 

 larvae tend to distribute themselves in approximately equal 

 numbers on the two sides of the aquarium which are most highly 

 illuminated. If, however, the light in one of the beams is of 

 greater intensity than that in the other, more larvae aggregate on 

 the side of the aquarium toward the brighter light. In other 

 words the larvae act as a sort of living photometer. It seemed 

 possible, therefore, to apply to these organisms the method 

 described by Mast (1907, 1917) for testing the relative stimulating 

 efficiency of light of various wave-lengths. 

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