336 KATHARINE FOOT AND E. C. STROBELL. 



years of investigation of one form forcing us to the conviction 

 that the chromosomes share a variability that is admittedly a 

 characteristic of other organs of the cell and a characteristic of 

 all organic structures. Such convictions as to the morphological 

 nature of the chromosomes made it impossible to have faith in 

 any hypotheses that were based on the type of individuality of 

 the chromosomes demanded by the theories in question. 



In a recent paper, Trow 1 gives an able and searching criticism 

 of one of these hypotheses and he has the sympathy of all sceptics 

 when he voices the pressing need of an accurate knowledge of the 

 chromosomes, especially of the maturation divisions where alone 

 can be found the cytological support essential to a foundation 

 for such a superstructure of imaginary architecture. This need 

 is further voiced by Bateson 2 in his report on a recent volume by 

 Morgan and his pupils. 3 Of the maturation prophases he says: 

 "That twisting takes place in many types, especially Amphibia, 

 is clear; but neither the figures reproduced from Janssens nor 

 the originals from which they are taken still less the very 

 fragmentary observations of both Stevens and Metz from 

 Drosopliila provide more than a slender support for this most 

 critical step in the argument. It is to be hoped that the authors 

 will before long tell us exactly upon what evidence they are here 

 relying." 



It is well known by cytologists that, with our present methods 

 of technique, an accurate knowledge of the maturation divisions 

 of Drosophila is impossible and one is led to suspect that this 

 ignorance as to the chromosomes leaves the imagination a 

 freedom that perhaps would not be possible if curbed by more 

 hard facts. 



1 "A Criticism of the Hypothesis of Linkage and Crossing Over," Journ. Gene- 

 tics, Cambridge, England, Vol. 5, No. 4, 1916. 

 'Science, N. S.. Vol. XLIV., No. 1137. P- 536- 

 3 "The Mechanism of Mendelian Heredity." 



