338 FORM AND STRUCTURE OF THE CELL [ch. 



sometimes it is adjacent to, and at other times it lies remote from, 

 the nucleus. The distribution of potential is very often symmetrical 

 and bipolar, as in the case described; but a less symmetrical 

 distribution often occurs, with the result that we have, for a time 

 at least, numerous centres of force, instead of the two main correlated 

 poles : this is the simple explanation of the numerous stellate figures, 



Haploid number of chr.'raosomes 

 Fig. 103. Summation diagram shewing the % number of instances (among 2,415 

 phanerogams and 1,070 metazoa), in which the chromosomes do not exceed 

 a given number. Data from M. J. D. White. 



or "Strahlungen," which have been described in certain eggs, such as 

 those of Chaetopterus. The number of chromosomes may be constant 

 within a group, as in the tailed Amphibia, with 12; or very variable, 

 as in sedges, and in grasshoppers * ; in one and the same species 

 of worm (Ascaris megdlocephala), one group or two groups of 

 chromosomes may be present. And remarkably constant, in 

 general, as the number in any one species undoubtedly is, yet we 

 must not forget that, in plants and animals alike, the whole range 

 of observed numbers is but a small one (Fig. 103); for (as regards 



* There are varieties of Artemia salina which hardly differ in outward characters, 

 but differ widely in the number of their chromosomes. 



