474 



SCIENCE 



[N. S. Vol. XXXIX. No. 1004 



Further Light mi the Conjugation of Paramoscium : 



L. li. WooDRurp. 



This paper will appear in the Jour. Exper. 

 Zoology, February, 1914. 

 Eea-ctions of Am^ba to Light : Asa A. Schaeffee. 



Perpendicular beams of white and of mono- 

 chromatic spectral light about 20 microns in diam- 

 eter were projected through the microscope after 

 being passed through 20 centimeters of water. 

 The beams were projected in or near the paths of 



The amoebas reacted to these beams of light be- 

 fore they came into contact with them as seen by 

 the human eye. In nearly all cases the reaction 

 was positive, that is, the amffiba moved toward 

 the beam of light. There was very little, if any, 

 difference observed in the reactions toward beams 

 of white and of the various spectral monochro- 

 matic lights. 



Brightly illuminated food particles were eaten 

 neither more nor less readily than when illumi- 

 nated evenly with the field; but when very slightly 

 illuminated, that is, when laid on a "dark spot," 

 the food object was sometimes not eaten. 



Amcebas frequently move toward a beam of 

 light in a curved path, finally coming into contact 

 with it; occasionally the curved path extends 

 around the beam of light so that the amceba en- 

 circles the beam for a greater or less distance 

 without coming into contact with it. If an amceba 

 has oriented itself with respect to a beam of light, 

 the beam may then be extinguished without caus- 

 ing a change in the direction of movement. Such 

 continuance of the direction of movement after an 

 orienting stimulus is removed is due to "func- 

 tional inertia, ' ' by virtue of which in this case the 

 amoeba tends to keep on moving iu a certain di- 

 rection after it is once started. No external 

 stimuli are necessary for continuing in a straight 

 path. The encircliug of objects and of beams of 

 light seems to be due to a balance between a 

 tendency to keep on moving in the original direc- 

 tion (functional inertia) and a tendency to react 

 positively to 'the stimulatuig object. 

 The Olfactory Sense of the Money Bee: Norman 



Eugene McIndoo. (Introduced by E. F. 



PhUlips.) 

 The Feeding Habits of Amblystoma Larvce: H. 



S. Burr. (Introduced by R. G. Harrison.) 



Normal Amblystoma larvae use the visual sense 

 in obtaining food when it is abundant. When the 

 food becomes scarce the larvae move slowly about 

 in search of it, nosing in the debris at the bottom 



of the aquarium. This characteristic reaction sug- 

 gests the use of the olfactory sense. 



Experimental evidence was sought to determine 

 how great was the reliance on this sense. Normal 

 larvae were tested with bits of motionless beef, 

 sand and live but motionless Daphnids. These 

 tests resulted positively — that is they snapped at 

 the source of the stimulus — in 91.6 per cent, of 

 the Daphnid tests and 38.7 per cent, of the sand 

 tests. The reactions to the beef were comparable 

 to those of the Daphnids. 



From eight 5-6 mm. larvffi the nasal placodes 

 were removed under a binocular microscope with 

 the aid of a pair of iridectomy scissors. When 

 they had begun to feed, they were tested by the 

 same methods as were the normal larvee. No re- 

 actions to beef or motionless Daphnids were ob- 

 tained. To sand they reacted positively in 60.7 

 per cent, of the tests. 



From eight 4-5 mm. larvae the optic vesicles 

 were removed. These were loaned to the writer by 

 Dr. Henry Laurens. These were tested with mo- 

 tionless Daphnids. They reacted positively in 

 98.8 per cent, of the tests. 



In the sand tests, the normal larvae as they grew 

 older showed an adaptation, in that the percentage 

 of positive reactions was greatly reduced in the 

 tests of the older individuals. The noseless indi- 

 viduals showed no such adaptation. 



Hence we may conclude that the larval Ambly- 

 stoma, while using the visual sense in obtaining 

 food when it is abundant, may in the absence of 

 moving food make use of the sense of smell, and 

 that this sense is of increasing importance to the 

 animal as it grows older. 



Experimental Analysis of Certain Processes in the 

 Food Vacuole of Bursaria: E. J. Ltjnd. (Intro- 

 duced by H. S. Jennings.) 



The Life History of the Bullfrog (Sana Cates- 

 leiana) : Albert H. Weight. (Illustrated with 

 lantern slides.) 



Because of its size, appetite, vocal accomplish- 

 ment and shyness, this species has received more 

 attention than any other American member of the 

 genus Sana. It frequents marshy bayous, button- 

 bush swamps, mill ponds, reservoirs, glacial or 

 sphagnaceous lakes and some marshy streams. In 

 first appearance this species is most influenced by 

 water temperatures. When the air reaches 68-75 

 (certainly 76-79), we may expect the appearance 

 of the bullfrog, provided the water bottoms are 



