470 



SCIENCE 



[N. S. Vol. XLI. No. 1056 



green. Green surroundings were nearly as effective 

 in bringing about this reaction, whereas red and 

 blue were much less so. When placed in a white 

 box certain individuals became green. The brown 

 color was assumed when a box lined with black 

 paper was substituted for a color box. The green 

 hue persisted with slight change for several hours 

 when the animal was in the yellow environment. 



When a lizard was blindfolded it remained 

 brown in the yellow box, and numerous tests 

 showed conclusively that the organs concerned in 

 receiving light stimuli, which induced a color 

 change in the skin from brown to green, were the 

 lateral eyes. 



The Absorption of Fat hy Fresh-water Mussels: 

 E. P. Churchill. (Introduced by Caswell 

 Grave.) 



The work was undertaken for the U. S. Bureau 

 of Fisheries with the object of ascertaining 

 whether or not aquatic animals use food which is 

 in solution in the water. Mussels were kept in 

 soap solutions made from olive oil, both unstained 

 and stained with Sudan III. Histological exami- 

 nation of such mussels and of controls revealed the 

 fact that fat is absorbed abundantly and carried 

 over the body by the blood corpuscles and plasma. 

 Sections of mussels kept in fat solutions short 

 periods, as 18 or 24 hours, showed such a heavy 

 loading of fat in the epithelium of gills, mantle 

 and foot that it seemed very probable that the 

 cells of such epithelium absorbed the fat directly 

 from the solution. Mussels with the valves wedged 

 open were suspended over the solution, so that only 

 the ventral part of the foot and mantle were im- 

 mersed, the mouth and siphons being above the so- 

 lutions. Examination after some hours of the 

 parts of epithelium so exposed showed more fat 

 than in the epithelium of other parts or in that of 

 the corresponding regions of the control. Pat can 

 be absorbed from solution by the epithelium of in- 

 testine and probably outer body walls. 



Vision in Floimders: S. O. Mast. 



Flounders, especially Faralichthys and Ancylop- 

 setta, simulate the background to a most remark- 

 able degree. The process of simulation involves 

 changes in shade, in pattern and in color. Since 

 all of these changes are controlled by stimuli re- 

 ceived through the eyes, the nature and the degree 

 of simulation of the background constitutes an ex- 

 cellent criterion of vision, in so far as this term 

 may be used in a purely objective sense. 



On the basis of this criterion it was found that, 

 in regard to shade and color, vision in fishes is es- 



sentially the same as it is in human beings. It 

 was also found that these animals distinguish be- 

 tween dots 2 mm. and 3 mm. in diameter respec- 

 tively, that they recognize dots 1 mm. in diam- 

 eter but that they do not recognize dots 0.5 mm. 

 in diameter. 



By means of a background consisting of a ro- 

 tating disk which contained alternate black and 

 white sectors, it was found that the fusion-rate of 

 images in flounders corresponds very closely with 

 that in the human being, indicating that in re- 

 gard to motion vision in fishes is as acute as it is 

 in man. 



On a background containing only gray or black 

 and white, no color is produced in flounders re- 

 gardless of the shade or pattern or the intensity of 

 the light. Simulation in color is consequently de- 

 pendent upon the length of the waves of the light, 

 not upon differences in its intensity. It therefore 

 strongly supports the contention that fishes have 

 color-vision. This is, moreover, supported by the 

 fact that flounders adapted to a given color tend to 

 select a background of the same color, and the 

 fact that this selection is of such a nature that it 

 can not be accounted for on the basis of difference 

 in the intensity of the light reflected by the dif- 

 ferent colors. Thus the contention that fishes have 

 color-vision is supported both by the reactions of 

 the animals and by the reactions of the chromato- 

 phores in the skin. 



Influence of Thyroid Ingredients on Division-rate 



in Paramcecium : R. A. Budington and Helen 



F. Harvey. 



Paramoecia of known ancestry were placed in 

 bacterial infusions of known composition. These 

 were kept on hollow slides in moist chambers in 

 the usual manner. To certain slides were added 

 equal amounts of dried thyroid glands taken from 

 types of each of the five main subdivisions of 

 Vertebrata. Besides each thyroid-treated line was 

 carried a control line, two progeny of a single di- 

 viding individual being used in the experiment. 



The number of individuals resulting from fission 

 in each line was counted each day; at the end of 

 six days the following were the data secured, each 

 figure being the average of three repetitions of 

 the same experiment: 



Fish thyroid 70.6 



Control 36.6 



Amphibian thyroid 111.3 



Control 20.0 



Eeptilian thyroid 225.3 



Control 24.3 



