678 



SCIENCE. 



[N. S. Vol. XXII. No. 569. 



tioni in the case of the late fourth and the 

 fiftn stage lobsters. 



EXPERIMENT VIII. 



Conditions: Mack background (similar results 



were seldom obtained on a white back- 



ground) ; sunlight bright ; 20 



late fourtli stage lobsters. 



Test. Lt. End. Mid-area. Dk. End. Cover. 



1 9 4 7 



2 11 5 4 Reversed. 



3 7 6 7 



4 9 3 8 



EXPERIMENT IX. 



Conditions: black background; medium sunlight; 



12 fifth stage lobsters. 

 Test. Lt. End. Mid-area. Dk. End. Cover. 



12 4 6 



2 2 3 7 



3 2 2 8 Reversed. 



4 13 8 



The results of these experiments may also 

 explain, to a certain degree, the facts which 

 appear through the observation of large num- 

 bers of the larval stages of Homarus vphen 

 confined and exposed to different light condi- 

 tions, as they may also interpret to some ex- 

 tent the behavior observed in the larval and 

 early adolescent stages of lobsters under nat- 

 ural conditions of environment. The first 

 three larval stages, when confined in the large 

 twelve-foot white canvas bags in which they 

 were observed, manifested at all times a 

 marked tendency to sink toward the bottom — 

 except perchance at night, when more active 

 swimming is observed in all the stages. This 

 tendency during the daytime could not be con- 

 trolled in any way. At night, however, it was 

 possible to evoke a seemingly positive photo- 

 tropic reaction from any of the thousands of 

 young larvae in the large canvas bags. This 

 was accomplished by means of an acetylene 

 light so directed against a certain area of the 

 white field of canvas that large numbers 

 would at once group themselves thickly about 

 the illuminated area, manifesting, in the case 

 of the third and fourth stages, such an effort 

 to come into the light area that they would 

 often throw themselves partially out of water, 

 causing thereby numerous surface ripples. 



Since, however, similar results could be ob- 

 tained when a black background was em- 

 ployed with the acetylene rays, and since the 

 results were not so definite when the incident 

 rays struck the water perpendicularly as when 

 they were thrown at an angle, it was assumed 

 that these reactions were not true phototro- 

 pisms, but were largely due to the effort on 

 the part of the young lobsters to move in the 

 direction of the incident light rays. This 

 phenomenon was better observable in the 

 fourth stage of Homarus, when the very 

 definite rheotropie proclivity, first clearly ob- 

 servable in this stage, could be entirely broken 

 up by introducing the incident rays either at 

 right-angles to or in opposition to the direc- 

 tion of the current. The fourth stage lob- 

 sters, however, even under the natural con- 

 ditions of light, swim actively at the surface. 

 It is not until the fifth stage that the bottom- 

 seeking and ' hiding-habit ' is fully established. 

 Philip B. Hadley. 

 Anatomical Laboratory, 

 Brown University, 

 October 10, 1905. 



an it;Lustration of the use of the wire- 

 basket METHOD FOR SOIL TESTING.^ 



The method of cultures in paraffined wire 

 baskets, for determining the relative agricul- 

 tural values of soils and for investigating the 

 effects of various fertilizers, which was de- 

 scribed in Bulletin No. 23 of this bureau, 

 consists in growing wheat seedlings in the 

 soils to be tested for from two to three weeks, 

 determination being made of the water lost 

 by transpiration and of the green and dry 

 weights of the plants at the end of the period. 

 Where differences between the various treat- 

 ments are developed it is found that the trans- 

 piration varies with the weight, being, there- 

 fore, a fair measure of growth.^ This meth- 

 od, which virtually furnishes a pot the walls 

 of which are composed of soil cemented with 

 paraffin, causes a uniform distribution of 

 roots in the soil and exhibits the effects of 



^ By permission of the Secretary of Agriculture. 



'^ See in this regard a paper on the relation of 

 transpiration to growth in wheat, about to appear 

 in the Botanical Gazette. 



