No. 464.] STUDIES ON PLANT CELL. VII. 581 



blastomeres which in consequence received a varying number 

 and assortment of chromosomes. Boveri then separated these 

 blastomeres and followed their independent development into 

 larval stages which exhibited marked differences in form that 

 could be correlated with the irregularities in the number of 

 chromosomes contained in each, thus suggesting that specific 

 chromosomes have specific functions. With this sort of evi- 

 dence accumulating from both the morphological and physio- 

 logical side it is not surprising that many biologists believe 

 that specific characters are actually held or are controlled by 

 chromosomes or groups of chromosomes. 



Such views of course presuppose that the chromosomes retain 

 a high degree of independence of one another and that variation 

 is expressed chiefly through different combinations of chromo- 

 somes and not by modifications of the chromosomes themselves. 

 Yet there is strong evidence of an actual mixing or interchange 

 of the idioplasm among the chromosomes. This possibility 

 which is of course contradictory to the view of the complete 

 independence of the chromosomes finds its chief support in the 

 close association of the pairs of chromosomes with the organiza- 

 tion of the reduced number of bivalent structures during synap- 

 sis. These pairs have been reported so intimately united as to 

 be actually fused. Allen (:O5) has described for Lilium the 

 union of two sets of chromomeres, one believed to be derived 

 from a paternal spirem and the other from a maternal, which 

 come to lie side by side during synapsis and unite to form a 

 spirem with a single series of fusion chromomeres. This single 

 (fusion) spirem later splits longitudinally and the two halves are 

 regarded as again representing maternal and paternal spirems 

 but there are evidently opportunities during the period of fusion 

 for significant reciprocal interaction between the two idioplasms. 

 This conception of the fusion of idioplasm from the two/ parents 

 is an old view which has been held by such well known biologists 

 as Hertwig and Strasburger. 



De Vries (: 03) has recently discussed the significance of the 

 pairing of chromosomes before the heterotypic mitosis in relation 

 to the theory of pangenesis. He conceives the paternal and 

 maternal chromosomes as coming together during synapsis in 



