710 



SCIENCE. 



[X. S. Vol. XXIII. Xo. 592. 



ward such as Jennings describes, for, accord- 

 ing to Rhumbler, the ectoplasm in front is 

 stretched between the vis a tergo and the 

 friction against the substratum, is weakened 

 and broken. The upper ectoplasm with a 

 broken front edge can hardly be imagined to 

 pull strongly upon the body behind it. 



It is not expedient in this article to go more 

 fully into the facts connected with this fa- 

 miliar phenomenon, which appears to be by 

 no means as simple an action as Rhumbler 

 supposes, when he compares it to the rolling 

 of a rubber tire by hand or to the creeping 

 of a drop of chloroform over a shellac-covered 

 surface. Both of the papers cited, however, 

 deserve the careful attention of every teacher 

 of biology who touches upon the subject of 

 Ammha and amoeboid motion, although the 

 conclusions of neither writer can be accepted 

 ■ without some modification. 



John H. Gerould. 



■ a culture medium for the zygospores of 

 mucor stoloniper. 



In the first edition of his ' Methods in Plant 

 Histology' Professor Chamberlain speaks of 

 the zygosporic phase of Mucor as being ' rarely 

 seen ' and requests information of anyone ob- 

 taining it. In the recent edition of the same 

 work he refers to the researches of Dr. Blakes- 

 lee and then gives directions for making cul- 

 tures for the zygosporic stage. The method 

 described is rather haphazard and the tone in 

 which it is stated indicates that the results 

 would be doubtful. 



During the past three months the present 

 writer has obtained the zygospores so fre- 

 quently that he now feels confident of being 

 able to secure them at any time within a week. 

 With proper conditions of moisture and tem- 

 perature, success is apparently dependent only 

 on the nature of the suhstratum. The sub- 

 stratum used is corn muffin bread, made, ac- 

 cording to the baker, after the following 

 formula : 



Corn meal 16 pounds. 



Flour 3 pounds. 



Lard 3 pounds. 



Salt 14 pound. 



Eggs 48 



Sweet milk 3 gallons. 



Baking powder 18 ounces. 



Half a dozen crumbs of this bread of the 

 size of a thimble in as many tumblers, will 

 yield on the average four or five cultures pro- 

 ducing zygospores in large numbers in from 

 five to seven days. The atmosphere should 

 be kept saturated, the temperature about Y0° 

 P. and darkness is favorable though not neces- 

 sary. 



A series of experiments have been made and 

 others are now under way to determine more 

 exactly the conditions of zygospore formation. 

 J. I. Hamaker. 



College Paek, Va. 



the effect of fertilizers on the reaction 



OF SOILS.' 



The effect of fertilizers on the reaction of 

 the soil has interested both the farmer and the 

 scientist for many years, but little experi- 

 mental work appears to have been done on the 

 problem, however. It is frequently held by 

 farmers that the continued use of fertilizers, 

 particularly of acid phosphates, and also pot- 

 ash salts and ammonium sulphate results in 

 the failure of the red clover crop, a result 

 which is attributed to the acid residues left 

 in the soil by the selective action of plants in 

 removing the essential elements from the salts 

 in which they are applied. While there can 

 be no doubt that certain fertilizing materials, 

 notably ammonium sulphate, will produce an 

 injurious degree of acidity, even changing the 

 reaction of an alkaline soil, the evidence with 

 regard to other fertilizers is not so positive. 



Only recently have methods giving definite 

 results been devised by which the total acidity 

 of a soil may be determined. It is possible 

 to detennine the acidity of soil within prac- 

 tical limits by the lime-water method,^ and I 

 have determined the present acidity of a 

 known naturally acid soil which has received 

 different fertilizing treatment, by this method. 



Dr. Thome, of the Ohio Experiment Sta- 



' Published by permission of the Secretary of 

 Agriculture. 



'Jour. Amer. Ghem. Soc, 26 (1904), 637. 



