Germ Cells of Leptinotarsa Signaticollis. 191 



whether Boveri is justified in combining the conception of the 

 permanence of the chromosomes and the doctrine that they are 

 individual or elementary organisms which lead a relatively inde- 

 pendent existence in the cell ; and furthermore that such a conclu- 

 sion does not necessarily follow from permanence in number, 

 form, and position in the nucleus, any more than that the cyto- 

 plasm is an individual organization because it grows and divides. 

 No more is gained in support of the hypothesis of chromosome 

 individuality by regarding the chromosomes as elementary and 

 relatively independent organisms which bear a symbiotic rela- 

 tionship to the cell, than that they are definite permanent parts 

 of a cell mechanism having a permanent, but not necessarily 

 independent existence in the cell. 



More recently Boveri ('07, p. 229) has given a definition of 

 chromosome individuality that is not quite so rigid, ''Was durch 

 den kurzen Ausdruck, 'Individualitat der Chromosomen' bezeich- 

 net werden soil, ist die Annahme, dass sich fiir jedes Chromosoma 

 das in einem Kern eingegangen ist, irgend eine Art von Einheit 

 im ruhenden Kern erhalt, welche die Grund ist, dass aus diesem 

 ruhenden Kern wieder genau ebensoviele Chromosomen hervorge- 

 hen, und dass diese Chromosomen iiberdies da, wo vorher ver- 

 schiedene Grossen unterschiedbar waren, wieder in den gleichen 

 Grossenverhaltnissen auftreben und dass sie dort, wo sie vor der 

 Kernbildung in characterischer Weise orientiert waren, diese 

 Orientierung bei ihrer Wiedererscheinung haufig in gleichen Weise 

 darbieten." This definition illustrates the general tendency to 

 depart from the older idea of the chromosomes being strictly 

 automatic individuals. 



It is this conception of automatism against which most of the 

 criticism of the chromosome hypothesis has been directed. The 

 observations of a number of investigators seems to show that the 

 chromosomes are represented in the resting stage between cell 

 divisions. Thus Bonnevie ('08) has shown that in rapidly dividing 

 cells (cleavage stages of Ascaris and root tip of Alium), although 

 the identity of the original chromosomes is lost in the resting nucleus 

 after each mitosis, each new chromosome arises by a kind of 

 endogenous formation from within and from the substance of its 



