470 DAVID H. DOLLEY 



and hence one dare not be influenced by any desired result. 

 The necessity of consciously following fixed rules of measure- 

 ment (juickly becomes impressed. 



Finally, the chief factor of variation is the nonmedian or non- 

 diametral section of both cell body and nucleus. To this the 

 following considerations apply. 



1. The structural indications of a median section are fairly 

 definite. However, as table 4 shows, the exactness of a median 

 section or the lack of exactness was not made a preponderant 

 requirement in the selection of a cell or in its rejection except 

 beyond a very plain appearance of disproportion. Cells were 

 chosen primarily because of certain objective characteristics 

 as described in the last section, and it was only required that 

 they show a fair approximation of a. median section. 



2. The diameter of the cross section of a nearly spherical body 

 varies very slowly for plane sections nearly median or diametral. 



3. The deviation from an actual diametral plane varies on 

 both sides of a certain mean. Considering the numerous possi- 

 bilities, not only of varying planes of section but of an eccentric 

 position of the nucleus, the only hope of approximation to an 

 average exactness lies in admitting cells whose elements it may 

 be are obviously slightly out of relative proportion, one way or 

 the other. No line could be drawn. 



4. At any rate, the smallness of the probable error indicates 

 that relative variations from the medial plane are probably not 

 large. 



Thfe suggestion of these points is due to Prof. O. D. Kellogg 

 of the Department of Mathematics. 



2. In the method of wax reconstruction 



Of the technical difficulties which it was found necessary to 

 overcome as far as possible, only two need be discussed in detail 

 as being especially important. 



1. The possible incompleteness of end, that is, conjugate 

 polar sections. This may apply to one or both poles of the nucleus 

 or plasma or both. In the two micra series, only two cells came 



