June 12, 1896.] 



SCIENCE. 



857 



knowledge is and remains throughout pro- 

 visional.' But inasmuch as Weismann has 

 undertaken to teach us 'just how the mole- 

 cules behave,' and since this is the only aim 

 of his essay, it would seem that all such 

 clamorings are entitled to some recognition. 

 Unless the food of determinants is ' Ein 

 ganz besonderes Saft,' one would think that 

 the soma might be able to supply it in 

 quantities large enough to cause the hungry 

 determinants and biophores to stop their 

 fighting. In all seriousness, it seems to me 

 that to class such a purely figurative and 

 imaginary ' struggle ' along with Darwin's 

 principle, as Weismann does, is to wholly 

 disregard the importance of evidence. 



3. The greatest objection to the all-suffi- 

 ciency of natural selection, which Weis- 

 mann, along with many others, recognizes, 

 is ' the fact of a simultaneous, functionally 

 concordant yet essentially diversified modi- 

 fication of numerous parts.' This objection 

 Weismann thinks he has removed by as- 

 suming that the determinants may vary 

 simultaneously and independently, and may 

 increase or decrease in size through ger- 

 minal selection. This does remove some of 

 the difficulties ; it furnishes, ex hypotheso, 

 the individual variations for personal selec- 

 tion, but the one great difficulty remains 

 untouched, viz., the combination of these in- 

 dividual variations into a functionally con- 

 cordant system. This difficulty, which is 

 really the only important one in this con- 

 nection, remains just where it was before 

 Weismann proposed his doctrine of ger- 

 minal selection. 



Weismann ably argues that there is in 

 certain quarters an evident tendency to 

 under- estimate the relative importance of 

 theories as compared with facts, and he 

 points out the great value of having sym- 

 bols or mental images of natural processes, 

 even though these symbols may not corre- 

 spond to reality. • Whether there are any 

 such things as biophores, determinant. 



germinal selection and the like, or not, it 

 is at least evident that a mental symbol is 

 better than mental vacuity, and that to 

 have conceived a process by which the de- 

 tails of evolution and inheritance can be 

 explained, even if it be a false conception, 

 is better than no conception at all. Prof. 

 Weismann is right when he says that there 

 is no just cause for criticism of his system 

 on the ground that it is purely imaginary, 

 provided if is ahuays so treated and understood. 

 It is only when he says that certain imagi- 

 nary processes must he so, as he does in this 

 as well as in former essays, that it is per- 

 tinent to remind him that we are dealing, 

 not with a system of necessities, but only 

 with a series of mental images, each one 

 of which may or may not correspond to 

 reality. 



I think it may well be doubted whether 

 such speculations are at present the most 

 profitable method of approaching the pro- 

 blems under discussion. Induction and 

 the test of conceivability are distinctly in- 

 ferior as scientific instruments to observa- 

 tion, experiment and deduction. Specula- 

 tion is valuable only as it is verified by ob- 

 servation and experiment and while the 

 solution of such recondite problems must be 

 approached from all possible sides, yet it 

 may be doubted whether it is more profita- 

 ble for one to continue to start more specu- 

 lations than a whole generation can run 

 down rather than to take part in hunting 

 down and verifying or rejecting his own 

 speculations. 



e. g. conklin. 



University of Pennsylvania. 



THE SMEETH SEPABATING APPARATUS. 



The tube devised by Harada for using 

 heavy liquids in separating the mineral 

 constituents of rocks has been modified by 

 Broegger, so as to obviate difficulties aris- 

 ing from the adherence of light and heavy 

 particles desired to be separated. This ap- 



