. A manual of zoology. Zoology. 62 GENERAL TRIXCIPLES OF ZOOLOGY Connected with this great functional importance of the chromosomes as the hearers of characteristics are two much disputed problems, (i) The 'individual- ity of the chromosomes.' This sees the persistent organization of the cell in the chromosomes, which persist between two cell divisions, but arc not recog- nizable as such because their substance is vacuolated and distributed through greater space. Of course this view does not conflict with the fact that they, like all living substance, undergo a gradual renewal, in which effete
. A manual of zoology. Zoology. 62 GENERAL TRIXCIPLES OF ZOOLOGY Connected with this great functional importance of the chromosomes as the hearers of characteristics are two much disputed problems, (i) The 'individual- ity of the chromosomes.' This sees the persistent organization of the cell in the chromosomes, which persist between two cell divisions, but arc not recog- nizable as such because their substance is vacuolated and distributed through greater space. Of course this view does not conflict with the fact that they, like all living substance, undergo a gradual renewal, in which effete parts are replaced by new and there is an increase of its substance without which a repro- duction of chromosomes by division would be impossible. (2) The theory of the functional diversity of the chromosomes. If the chromosomes carry the characteristics, it is more probable that each one does not contain the germs of all the peculiarities of the organism; rather there is a division of labor by which the separate peculiarities are distributed among the different chromosomes. This view is supported by the fact that there is, in numerous instances, a morpho- logical differentiation between them (dilTerences insi2e,sha])e, staining qualities). That in the last analysis each category of characters consists of at least two lines (male and female) is shown by the fact that, as is ex- plained in the section on fertilization, half of each nucleus is derived from the father, half from the mother. Nuclear Fragmentation is to be distinguislied from direct division; l-)y it the nucleus becomes broken up into a few or numerous parts. Such nuclear fragmentation is not rare in the Lifusoria but it occurs occasionally in Metazoa (giant cells of bone marrow—fig. 24—osteoblasts, certain stages of the genital cells). It is explained as follows. There normally exists a certain size relation between nuclear mass and protoplasmic mass. With greater cell activity, as with Infusoria which have lo
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
