635 



others, and in entire concordance with our knowledge of the general 

 behavior of the chromosomes in the germinal cycle, it is clear that the 

 nucleus of a germ cell cannot consist of a paternal and a maternal 

 gonomere after the synapsis stage. The synapsis stage effects the pair- 

 ing of each paternal chromosome with a maternal chromosome in 

 those cases where there is an even number of chromosomes; in those 

 cases where there is an uneven number the odd chromosome does not 

 unite with any other, as I first showed for four species of Hemiptera, 

 and as Rosenberg has recently confirmed by the study of the chro- 

 mosomes of a Drosera hybrid. Each bivalent chromosome then con- 

 sists of a paternal and a maternal element. The reduction division 

 separates these two components of each bivalent chromosome. There- 

 fore nucleus of an ovocyte or spermatocyte of the first order cannot 

 be divided into two gonomeres; and therefore, also, the mature ovotid 

 or spermatid can have only univalent chromosomes. 



It clearly follows from this, then, that if Cyclops brevicornis has 

 in the ovotid bivalent chromosomes, each a conjoint of a paternal and 

 a maternal, this Crustacean would present unique chromosomal phe- 

 nomena. And because entirely différent results have come from much 

 patient and careful observation on the part of others, it would seem 

 probable that the recent observations of Prof. Haecker on Cyclops 

 may be in error. And the three vertical diagrams which he gives on 

 Tafel 12 of his last paper to represent three difi'erent types of chromo- 

 somal behavior, may well be reduced to one. 



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42* 



