62 



XLIV. R. V. Allison. " A Note on the Protozoan Fauna 

 of the Soils of the United States/' Soil Science, 1924. 

 Vol. XVIII., pp. 339-352. 



The examination of a series of soil samples from widely 

 divergent points in the United States shows a considerable uni- 

 formity in the distribution of the more important of the three 

 protozoan sub-phyla, Flagellates, Ciliates and Rhizopoda. The 

 range of type genera was found to be quite similar to that holding 

 for English soils. 



From quantitative studies upon these same samples it is 

 suggested that a possible explanation of the divergent conclusions 

 of English and American investigators may be found in the 

 difference in the extent of the protozoan fauna in the respective 

 materials investigated. Thus the biological phenomena which 

 follow the partial sterilization of the soil and which have been 

 so extensively studied by both groups of investigators, though 

 admittedly similar in nature, may have as their fundamental basis 

 groups of organisms of quite diverse natures. 



XLV., XLVI. D. W. Cutler and L. M. Crump. " The 

 Rate of Reproduction in Artificial Cultures of Colpidium 

 Colpoda. Parts II. and III." Biochemical Journal. 

 1923-24. Vols. XVII., XVIII., pp. 878-886, 905-911. 



The rate of reproduction of Colpidium colpoda has been 

 tested in cultures derived from one or more animals isolated into 

 small volumes of fluid. It is shown that in the main such cultures 

 are comparable with mass cultures. 



The allelocatalytic effect, described by Robertson, has been 

 tested and found not to obtain with Colpidium when isolated 

 into fluid whose volume varies from 0.5 to 8.5 mm. A few 

 experiments are given in support of the contention that the rate 

 of reproduction can be accelerated by the addition of small 

 quantities of crushed bacteria or protozoa. 



Experimental evidence is given that the number of divisions 

 Colpidium colpoda undergoes in definite periods of time is 

 intimately connected with the size of the bacterial population. 



Further investigations on the relation between the size of the 

 inoculum and the rate of reproduction demonstrates that the 

 number of divisions steadily decreases as the number of animals 

 inoculated increases. 



(c) FUNGI. 



XLVII. J. Henderson Smith. "On the Early Growth 

 Rate of the Individual Fungus Hypha." The New 

 1'hytologist. 1924. Vol. XXIII., pp. 65-78. 



The fungal hypha elongates at the tip only. The rate of 

 elongation is at first very slow, but steadily increases as time 

 passes, and eventually reaches a maximum value many times 

 greater than the initial rate, and this is maintained for a long 

 period. Different individual hyphae show considerable differences 

 in the actual rate and in the manner of development, but the 

 majority behave similarly under similar circumstances. Although 

 n in. reasea as tin- length increases, the rate of extension is not 



