m'clung: chromosomes of anasa tristis. 369 



nature of the nuclear body, they assume that it is a plasma- 

 some. "As the presence of a plasmasome in the nucleus at 

 these stages is the typical phenomenon familiar in all known 

 forms (its absence being most exceptional), we feel justified 

 in interpreting the structure we find in the resting nucleus as 

 a true plasmasome, and not an odd persisting spermatogonial 

 chromosome, i. e., chromosome nucleolus." (Foot and Strobell, 

 '07, p. 284.) Further, the smear method does not give precise 

 and accurate pictures of the chromosomes. The variation in 

 size, owing to the different thicknesses of the smear and amount 

 of spreading, is very extensive, as may be seen by a com- 

 parison of the photomicrographs of Foot and Strobell. Com- 

 pare, also, figures 21-26, plate LXX, which represent smears 

 of cells in the same stage. Not only may the entire groups of 

 chromosomes in similar cells vary as three or four to one, but 

 the members of one cell may suffer unlike expansion or con- 

 traction to a similar extent, if the conditions of drying are 

 variable, due to the thickness of the smear film. There is but 

 one advantage of the smear method over sections, and that is 

 that it presents all the elements of the cell in one plane, so that 

 their entire outline is visible for studying and photographing. 

 It is a method that should be used in connection with sections, 

 and from the beginning of my work I have utilized it con- 

 sistently and with great profit in this way. I therefore speak 

 of it as a warm friend and advocate, but at the same time I 

 realize its limitations and am convinced that it should not be 

 used to the exclusion of all other methods. 



Foot and Strobell have employed photography alone as a 

 means of presenting illustrations of their material, and it is 

 assumed by them that if a thing can be photographed it must 

 necessarily be a true picture of normal conditions. This I 

 consider to be a decided fallacy. A photograph is an inter- 

 pretation by the observer, just as is a drawing. The personal 

 factor is no more absent from one method of illustration than 

 it is from the other. Photographs may present with greater 

 fidelity the details of structure in an object, but the choice of 

 the object and the nature of details are at the command of 

 the photographer. It is possible, especially in smear prepara- 

 tions, to select cells that will illustrate almost any condition 

 and to photograph them. The highly interpretative character 

 of the photograph is illustrated admirably by the present con- 



