320 LESTER W. SHARP 



tions only through the omission of the finer détails and an incomplète 

 avoidance of schematism. Only at prophase do we find anything ap- 

 proaching the condition shown in his fig. 5-2 a and 52 ^ (12 Z'), which are 

 given as anaphase aspects. 



The séries of figures given by Fraser and Snell (it) is also very 

 incomplète in the absence of the early stages and détails of alveolization. 

 One would interpret their fig. 4-6 as representing a telophase split only 

 after considérable hésitation, 



The figures of Bonnevie (08, 11) and of Dehorne (ii) are apparently 

 schematizations of the occasional spiral aspect of the alveolar bands. 



AU the above having been said, we insist upon one fact, a fact obvious 

 when the détails are known, that whatever be the condition at telophase and 

 very early prophase - whether there be irregular alveolization, regular 

 alveolization, or a fairly even longitudinal division of the chromosome — it 

 has nothing whatever to do with the true split which occurs in the thin 

 thread at prophase. 



The interphase and resting stages hâve been most fully figured by 

 LundegArdh {i-2b, plate 17). Concerning thèse figures it should be said 

 that such impressions as they convey hâve frequently been gained from our 

 material, but never from préparations which proved to be of value for cri- 

 tical study. Such absence of détail from properly stained material is not 

 easily understood. The figures which Fraser and Snell (ii) give as resting 

 nuclei are far too small and devoid of détail to be of value in interpreting 

 thèse difficult stages. 



Having established the time of the splitting in Vicia, its nature must 

 now be considered. 



Strasburger held strongly to the opinion that the splitting is initiated 

 by the division of definite morphological units or chromomeres arranged 

 in a séries along the thread. This was denied by Grégoire and Wygaerts 

 (o3) for Trilliitm, Martins Mano (04) for Phasaeolus and Solanum, and by 

 Grégoire (06) for Alliiim. In 1907 Strasburger again described chro- 

 momeres in Pisiim, and the follovving year Grégoire (08) made answer. 

 Bonnevie (08) and Stomps (10) found no chromomeres in Alliuin and 

 Spinacia respectively. In igii Strasburger still retained his former idea. 

 In his work on Najas Mûller (12) again described chromomeres, but 

 modified the former théories by stating that the portions of the thread be- 



