158 ROBERT T. HANCE 



because they appeared impossible of interpretation. Since the physio- 

 logical character of the chromosomes are as yet undetermined and 

 since at present our only method of forming a conception of the ac- 

 tivities of the chromatic material is through morphological studies 

 in the broadest sense, it scarcely needs to be pointed out that un- 

 critical wotk of the sort discribed is not likely to be productive of 

 results. 



It is quite true that when we have determined the behavior 

 of somatic chromosomes we are not a great deal nearer the solu- 

 tion of development for it seems quite evident that the ultimate 

 analysis of this problem must be largely a chemical one. But, 

 since chemical studies of such nature are impossible at present, 

 morphological investigations may indicate the lines which future 

 research may advantageously follow and even may indirectly, 

 through a careful study of the division phenomena in many 

 tissues of a large number of plants and animals, lead to an under- 

 standing of the physiology of the cell. 



TECHNIQUE 



Preparation oj tissue. Probably more inaccuracies in cytologi- 

 cal work have resulted from the use of poorly prepared material 

 than in any other way. This is particularly true of mam- 

 malian studies, and, with the possible exception of the investiga- 

 tions of Winiwarter, the work of other mammalian cytologists is 

 practically valueless and will have to be carefully repeated. We 

 have definite criteria now with which to judge our preserved ma- 

 terial, namely the studies on the living cell (Lewis and Robert- 

 son, '16). Consequently the cytologist who attempts to unravel 

 clumped chromosomes and to draw conclusions on the supposi- 

 tion that he knows the chromosomes as they are, not only in- 

 vites destructive criticism of his work, but adds nothing to our 

 knowledge and wastes our time. 



The method that has given excellent results has already been 

 described at length (Hance, '17 b). In brief it is as follows: 



1. Obtain fresh specimens from as many different animals as 

 possible so as to be sure of obtaining one or more in a 'cycle of 

 division. ' 



