MULTIPLE CHROMOSOMES 557 



Meek has done good ser\'ice in pointing out the facts, but it is 

 unfortunate that he should push his generalizations so far upon 

 a limited experience. Very different are the methods and 

 conclusions of Delia Valle. 



Variations in size, according to Delia Valle, fall within the 

 limits of observational error and are of the order of size varia- 

 tions of droplets in an emulsion. Correspondence in size between 

 chromosome and the nucleus finds its explanation in the physical 

 condition of adsorption. As in the case of numbers, the appeal 

 is from an explanation based on order of determinable character 

 to one in which only the chance circumstances of physical rela- 

 tions obtain. Opposed to this conception stand all the careful 

 investigations in which definite size relations are shown to be 

 preserved, not only in a single series but in a duplicate one. 

 Within this occur occasional inequalities, which, in turn, are of 

 definite character, pertaining to certain chromosomes and so 

 recurring as to be accounted for most readily through genetic 

 continuity and chance distribution and recombination. Upon 

 this point again the circumstances in H. viridis offer important 

 evidence. The smaller members of the complex form an ascend- 

 ing series which, in class 1, is continued without breaks through 

 the larger members. But In the remaining classes there are sharp 

 breaks in seriation of exactly the same character in all the cells of 

 the individual, entirely beyond the range of observational error 

 and past the possibility of chance variation. The conditions are 

 altogether of the character of order and system common to liv- 

 ing structures and foreign to purely physical phenomena. The 

 material upon which the Italian author worked is not nearly so 

 favorable for size determinations as are many other kinds, be- 

 cause of the great length and irregular contour of the elements, 

 but even here much more accurate results could have been ob- 

 tained by the exercise of .such care as was employed by Meek. 

 From some studies being pursued in this laboratory by Mr. 

 Parmenter I feel certain that the Amphibia are no less exact in 

 their size relations than are other groups of animals. 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 2 



