1909] YAMANOUCHI— MITOSIS IN FUCUS 187 



to end. If we apply a modern 



maternal 



ananged in early prophase, not in parallel threads, but with the 



form 



onema 



during which there probably takes place a close association of the 

 chromatin of the two origins. In this case, the pachynema and 



must 



chromatin 



synapsis passes directly into the diakinesis stage. The two elements 



chromosomes 



effecting what may be regarded as a reduction. Generally in Fucus 



mi 



second division does not occur even in late anaphase of the first 



may 



daughter nuclei, asintl 



Neglecting for a moment the many points which differ in particu- 

 lars, the results in Fucus, namely, that the chromosomes emerging 

 i'rom synapsis show the reduced number, and that the reduction has 

 taken place by an end-to-end fusion of sporophytic chromosomes, 

 agree in essentials with the views published by Farmer and Moore 

 (6, 7), Schaffner (21, 22), Mottier (is, 16), and Strasburger 

 ( 2 5), and by one group of zoologists, such as vom Rath (17). 



RiicKERT (20), and Montgomery (13, 14). 



Regarding the origin of bivalent chromosomes, however, the 

 author is fully convinced of the correctness of the interpretation that 

 ln the majority of cases now investigated, two independent threads 

 °nginate in early prophase and become associated side by side in 

 ^apsis, and that when the two threads emerge from synapsis they 

 the ^0 elements of the bivalent chromosome. Such cases were 

 ^arly established by Gregoire (10, 11,12), Berghs (3, 4), A LLEN 

 2 2) ' Rose nberg (18, 19), and some others, including the author 

 haas ^ (30, 31). The author, in a forthcoming paper on sporo- 

 genes ls in Qsmunda cinnamomea has reached the same conclusion 

 15 h as the latter group of investigators. The results in Fucus, how- 

 ^ er > are not deniable. It is not inconceivable that there are two 

 1Stlnct ^es of arrangement of sporophytic chromosomes at synapsis. 



form 



