SOMATIC CHROMOSOMES IN VICIA 3l3 



even in différent portions of the saine chromosome, fig. 5b. Again at this 

 stage is frequently seen a spiral aspect. Fig. 6-9 sliow stages in the forma- 

 tion of the zigzag threads; in each case the nucleolus is not included in the 

 thin section from which the drawing was made. 



The almost entire absence of thèse stages from the accounts of many 

 other writers is noteworthy, since they constitute évidence of the very 

 highest importance in interpreting the splitting of the chromosomes. 

 Although tliey form most striking aspects in the early prophases of Vicia 

 they do not occur in the accounts of Fraser and Snell (ii) and of 

 LuNDEGÂRDH (oQ, lo, I2b, c) , who hold that the resting reticulum gives 

 lise to threads double from the first, the duplicity probably corresponding 

 to that which they find at telophase. Since the works of (jrégoire and 

 Wygaerts (o3) and of Grégoire (o5) in which thèse phenomena were des- 

 cribed, the nearest approach to a représentation of such stages is given 

 by NËMEC (lo), who shows in his fig. in5 of Alliiim the condensation 

 of régions of the net to form irregular vacuolate bands ciuring prophase. 

 MuLLER (12) believes the threads are formed by direct condensation 

 without passing through the zigzag stage above described. 



According to Della Valle (og, 12) the thin threads of the prophase 

 are due to an end to end association of liquid crystals, whose curved form 

 results in the spiral appearance of the threads. He draws many compari- 

 sons with similar phenomena observable in liquid crystals artificially pro- 

 duced, erythrocytes, cell granules of varions kinds, and even nuclei. But 

 it is noteworthy that in the case of the organism studied fSalamajidraJ the 

 stages necessary to denionstrate the phenomenon are not figured. This 

 fact, taken together with the détails of thread formation from a band as 

 hère presented, prevents a very serions considération of the theory in the 

 simple form stated by Della Valle. 



The remarkable figures of Bonnevie (08, 11) without any doubt re- 

 present schematizations of the zigzag and often spiral appearance of the 

 early prophase figures, while those of Dehorne (ii) seem to hâve been 

 formed through the application of a similar method to the earlier conden- 

 sing bands. 



In Primula Digby (12) states that the chromosomes are formed by 

 the stringing together of homogeneous beads of chromatin, which stands 

 in agreement with the aspects Lundegârdh {12a) has seen in living ma- 

 terial of Vicia. Béer (12) briefly describes the concentration of the reti- 



