mack: dimensions of chromosomes. 121 



the number to be 24 in the cells of the various tissues, agreeing 

 with the number in the spermatogonial and primary sperma- 

 tocyte as given by the *Schreiners and Meek. Baumgartner 

 seemed to discover a difference in the form of the chromosomes; 

 Sutton a difference in size; and Meek a difference in measurements. 

 I wish to apply these tests to the somatic cells to determine 

 whether by a study of the form, size and dimensions we can ar- 

 rive at some definite conclusions concerning their relation to the 

 germ cells. 



I made a careful study of several hundred cells, and made 

 measurements of the chromosomes of most of them, and com- 

 pared those of the neuroplasm with those of the ectoplasm, the 

 muscle, the connective tissue and the pigment tissue. In all 

 cases I found them grouped about the equatorial plate in an ir- 

 regular manner. They are always in the U or V shape with the 

 spindle fibres attached one at the vertex of each chromosome. 

 These fibres are almost invariably attached in such a way that 

 the two arms of the V are of unequal length. 



As will be seen in figs. 4 and 5 the chromosomes in the same 

 cell are often irregular in outline, thick in some places and thin 

 in others. The chromosomes of the connective and muscular 

 tissue, while resembling each other in form and size, have some 

 differences and are not like those of other tissues. Those of the 

 muscular tissue are rough and short, while those of the connective 

 tissue are short, thick and smooth. Those of the pigment cells 

 are always very smooth and also much longer in proportion to 

 their breadth and can invariably be distinguished by their high 

 staining qualities, always being a bright violet in the preparations 

 studied. 



Some of the chromosomes differ in size because of difference 

 in tissue and also because of the difference in the age of the tissue, 

 as will be brought out more definitely a little later. They also 

 differ in size in individual cells but the difference is so slight in 

 any one cell that it is difficult to determine without accurate 

 measurements, neither is it possible to arrange them in any such 

 system as some authors have done, of three small, two medium 

 and five long ones, etc. Without a doubt they have an individ- 

 uality and "these various shapes are an expression of the indi- 

 vidual characteristics of the various chromosomes" as fBaum 



* A. and K. E. Schreiner. Neue Studien uber die Chromatinreifung der Geschlechts- 

 zellen. 



fBauingartner ("04). Some New Evidence for the Individuality of the Chromosomes. 



