M'CLUNG: CHROMOSOMES OF ANASA TRISTIS. 337 



That would make the number of nuclei with no accessory 537, 

 which is slightly larger than the number with the accessory. It 

 has been pointed out that the nuclei which were cut in two 

 equal parts might be counted as two. This would add to the 

 number of cells which did not contain an accessory. Consider- 

 ing this source of error the nuriiber of cells of each kind may 

 practically be considered as equal. There can be no doubt 

 as to the occurrence of two kinds of spermatids which develop 

 into spermatozoa, one containing one more chromatid, the ac- 

 cessory, than the other; and from the evidence presented we 

 feel justified in concluding that the two kinds of spermatozoa 

 occur ih equal numbers. 



III. A COMPARISON OF THE RESULTS OF STUDIES UPON 

 CHROMOSOMES OF ANASA. 



BY C. E. M'CLUNG. 



1. Methods. 



The methods of an investigator are a very important factor 

 in arriving at conclusions, and it is quite possible to secure 

 diametrically opposite results upon the same material by 

 varying the technical processes. It will, therefore, be neces- 

 sary to consider the methods of preparation and study em- 

 ployed upon Anasa. Paulmier, Montgomery, Wilson, Lefevre, 

 McGill and Pinney fixed their material with Flemming's fluid, 

 corrosive-acetic mixtures, Bouin's fluid and various other 

 cytological reagents. This material was then sectioned in 

 paraffin, and stained, principally with the iron alum — hsema- 

 toxylin stain of Heidenhain. The slides thus prepared by 

 Paulmier, Wilson, Lefevre and Pinney are beautiful examples 

 of cytological technic and leave little to be desired in delicacy 

 and precision. A considerable number of the slides sent me 

 by Professor Wilson and Professor Lefevre are prepared ac- 

 cording to the methods of Foot and Strobell, so that I have 

 been able to study the material under their conditions, al- 

 though, unfortunately, their own preparations have not been 

 accessible to me. Since the entire case of these investigators, 

 as opposed to all their fellow workers, rests upoti their owh 

 peculiar methods, it seems desirable to consider in detail the 

 technic upon which they rely. 



The usual methods of cytologists are dismissed with prac- 

 tically no consideration, and instead of fixing the material, it 



