190 Harry Lewis Wieman. 



in a linear series so that a division in a plane including the axis of 

 a chromosome, halves each particle in it, while on the other hand 

 a division at right angles to the axis separates whole chromosomes. 

 Further discussion of this question need not be entered into here 

 for it is evident that so long as nothing definite is known of the 

 arrangement or significance of the component parts of a chromo- 

 some, the absence of the so-called quantitative division need not 

 be considered of especial importance. Similar conditions in other 

 forms may be of much wider occurrence than is at present sup- 

 posed. 



It is seen from this account that there does not seem to be a 

 true synapsis or complete fusion of chromosomes in the forma- 

 tion of the spireme of the prophase of the first maturation division. 

 The duality of the series is perfectly evident and the frequent 

 instances where the components are more or less separated 

 speaks for the absence of fusion. The only fusion that has oc- 

 curred is in the disappearance of the transverse furrow which 

 in synizesis divided each chromosome so as to produce twice the 

 somatic number of segments (Figs. 50 and 51) . The disappearance 

 of this furrow is only temporary, for it reappears in each bivalent 

 chromosome after the spireme has broken up into the reduced 

 number of segments (Figs. 52 and 53). 



Cases like Fig. 49 showing the first step in the re-formation of 

 the spireme after the resting period, suggest very strongly that 

 the biserial arrangement of the chromosomes on the parallel linin 

 threads connected with the chromatin nucleus persists through 

 the resting stage. The evidence for what has been called 

 ''prochromosomes" is not very marked; the chromatin being 

 represented by irregular masses whose number could not be de- 

 termined with any exactness. Evidence along this fine has been 

 urged by many workers in support of the conception that the 

 chromosomes are permanent cell structures. Boveri ('04) in his 

 stating that the chromosomes are individual elementary cell 

 organisms "die in der Zelle ihre selbstandige Existenz fiihren," 

 has perhaps gone to the extreme in developing the individuality 

 hypothesis; and Rabl ('06) has expressed a similar view. 

 ' Harper ('05) has pointed out that it is somewhat questionable 



