136 LOUISE B. WALLACE. 



the two arms are carried to opposite poles of the spindle, we 

 plainly have a longitudinal or equational division. It is also of 

 interest here that in this mitosis the rod-like accessory chromo- 

 somes divide equationally. To sum up, then, the first matura- 

 tion division occurs at a point corresponding to the bend of the 

 spireme loop and is a reductional one ; the second maturation 

 division passes along the line of the longitudinal split of the 

 spireme loop and is an equational one. 



Individuality of the Chromosomes. 



Every living organism, whether plant or animal, single-celled 

 or many-celled, is regarded as an individual notwithstanding the 

 fact that each one is so lacking in stability that, in its metabolic 

 processes, it has frequently been compared to a whirlpool into 

 which and out of which new particles are constantly streaming. 

 Again, in the ontogeny of a Metazoan, the cells of which it is 

 composed and the cell-nuclei are supposed to be continuous from 

 one cell generation to the next. When, however, we come down 

 to one of the most important nuclear elements the chromosome, 

 there has been much difference of opinion in regard to individu- 

 ality, some claiming that when a given chromosome disintegrates 

 and spreads out in a reticulum in the resting stage, the same 

 chromosome does not reappear in the succeeding mitosis but that 

 the chromosomes are formed anew each time. Ever since Rabl 

 ('85) strongly supported by Boveri ('87, '88) and Van Beneden 

 ('83) maintained that the chromosomes do not lose their individu- 

 ality at the close of division but persist in the chromatic reticulum 

 of the resting nucleus, scores of workers have brought forward 

 evidence either for or against this theory. In a recent paper by 

 Foot and Strobell ('07 (<)) we read as follows : If we mean by 

 "Individuality of the Chromosomes" merely that we recognize 

 certain characteristics of size and form in some of the chromatin 

 units called chromosomes and that there is a frequent repetition 

 of these forms during different stages of development, then we 

 may claim that the chromosomes of Anasa tristis unqualifiedly 

 support the theory of the " Individuality of the Chromosomes." 

 But on the other hand, if by " Individuality of the Chromosomes ' 

 we claim their morphological continuity, that several or even 



