-•t 



662 C. E. McCLUNG 



SYNAPSIS PERIOD 



As has already been stated, we have no exact knowledge of 

 the changes taking place at this time. Their significance is un- 

 questionably great, and no pains should be spared to determine 

 their character fully. But even were they completely understood 

 we should still be lacking a continuous picture of well defined, 

 individual chromosomes throughout their entire history for, 

 succeeding the synaptic phase, comes a period when the chromo- 

 somes become very diffuse and their outlines with difficulty 

 distinguishable. We may not therefore hope to be able to recog- 

 nize the chromosomes in a compact and sharply defined form 

 through the various stages of their development. That they 

 are however morphologically continuous seems to me unques- 

 tionably evidenced by the fact that, succeeding all these involved 

 and complicated changes, there is finally a reappearance of the 

 same series of elements in the same cell, with the one difference 

 that instead of twenty-three single chromosomes in the Acrididae 

 there are now eleven pairs, plus one chromosome that continues 

 on unchanged. I believe, therefore, that we have every reason 

 to consider that in the prophase of the first spermatocyte we are 

 dealing with the same chromosomes that came into the cell when 

 it was produced by the division of the last spermatogonium. 

 Whether union was made side by side or end to end in the 

 synaptic period has not been determined, but it is very clear 

 that in the last prophase the chromosomes show undoubted 

 telosynapsis. 



CHROMOSOMES OF THE FIRST SPERMATOCYTE PROPHASE 



a. Evidence for chromosome individuality 



Fundamental to the entire conception of chromosome relations 

 is the belief that we are dealing with persistent morphological 

 entities. If this be not true then the whole question of the con- 

 stitution of the chromosomes and the method of their division 

 is of no theoretical importance. That they are of this definite and 

 significant character is however evidenced in many ways. In 



