No. 425.] NOTES AXD LITERA TURE. 405 



would represent the weight of the fluids which leave the body on 

 evaporation at this temperature. The relation 



M- F 



M 



= (7 



is known as the fluid coefiicient and signifies the percentage of fluids 

 in a unit of weight of the living insect body. Experiment shows that 

 the smaller the fluid coefficient the lower lies the normal congealing 

 point of the fluids. The critical point is also influenced by the fluid 

 coefficient, but this influence cannot be stated in general terms till 

 the composition of the fluids has been further studied. Time also 

 influences the critical point. If the temperature (t) to which the 

 insect is undercooled coincides at the same rate of cooling with the 

 critical point (-^'1), the juices at once begin to congeal (i.e., time = o)\ 

 but -if t does not coincide with Ki, the congealing of the fluids is 

 delayed in proportion to this difference (A'l — t). 



Undoubtedly Bachmetjew's results are of a far-reaching character 

 and will ultimately form the basis for important work along theo- 

 retical lines in physiology, and for practical applications of great 

 moment (in economic entomology, e.g. !), for they throw light on the 

 geographical and climatic distribution of organisms, the resistance of 

 animals and plants to cold and heat, and the problems of anabiosis. 

 That Bachmetjew himself is very sanguine concerning the results 

 that may ultimately flow from his work is apparent when he says . 

 " Es eroffnet sich somit ein ganz neues Gebiet fiir die Forscher, und 

 wer weiss, ob die Zeit nicht nahe ist, wo man den marchenhaften 

 hundertjahrigen Schlaf auch bei Menschen kiinstlich hervorrufen 

 konnte ! Die Insekten wenigstens bieten die Moglichkeit dazu." 



W. M. W. 



An Important Paper on Phoridae. — Theodor Becker, of Liegnitz, 

 Prussia, has recently published a work ^ of 100 pages, with five 

 plates, on the family Phorida;, which deserves notice among zoolo- 

 gists in general because it is one of the finest pieces of systematic 

 work that has been published on the Diptera. 



The family Phoridae includes only small species, generally from 

 two to four millimeters in length, which do not offer to the observer 

 with a hand lens a satisfactory series of specific characters. The 

 genus Phora was early described and generally recognized from its 



1 Abhandliini:;en der k. k. zool.-botan. Gesellschaft in Wien, Bd. i, Heft i, 1901. 



