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C. W. METZ. 



metaphase. Fig. 4 shows the closer association of late prophase. 

 The intimate association of the early prophase is represented in 

 Figs. 5 and 6. In the former each of the long bodies (numbered 

 i, 2, 3, 4, 5) is composed of four thread-like chromosomes, closely 

 approximated side by side. This nucleus is almost entire, but the 

 body numbered 2 appears to be cut at the point where the number 

 is placed. Number 6 is presumably the set of small sex chromo- 

 somes. Fig. 6 represents a slightly earlier prophase in which the 

 threads are somewhat more attenuated. The nucleus here is cut 

 and lies in two sections, so that only three or four of the long. 



o * 



tetravalent bodies are complete. These show the same intimate 

 association of homologous threads, however, as do the similar ones 

 in Fig. 5. In both of these figures and in other prophases of a 

 corresponding stage the association of homologues is so close that 

 the individual threads can only be distinguished here and there. 



As the figures indicate, the four threads of each body in the 

 early prophase appear to be associated in equal degree. I can find 

 no indication of a closer association of sister elements than of non- 

 sister elements within the tetrad. 



It appears, then, that in these cases the force which brings 

 homologous chromosomes together is exerted equally between the 

 respective members when four are present. 1 This agrees with the 

 observations of Holt on Ciilc.r if we accept the latter of the two 

 views suggested above that the chromosomes conjugate in three 

 groups of homologous individuals, without any distinction between 

 sister and non-sister homologues. 



Possibly this equivalence of association applies only to the gross 

 relationships and does not represent the actual interrelations be- 

 yond the limits of visibility. That is a question, however, which 

 can hardly be answered by a study of somatic cells. In the case 

 of synapsis in the germ cells it may be possible to answer it by 



i- The question might be raised here as to whether these chromosomes 

 actually come together, or whether they owe their association to successive 

 divisions of the orginal prophase chromosomes in situ. The latter view 

 involves the assumption that such cells do not multiply, and that each case 

 represents an independent origin from a diploid cell. The evidence is against 

 such an assumption, for all stages of division (prophase, metaphase, anaphase, 

 etc.) may be found in these cells, and in some pieces of tissue nearly all of 

 the cells are of the same multiple chromosome type (e.g., in Fucellia). 



