CHROMOSOME STUDIES 251 



4. Does synapsis lead to partial or complete fusion of the con- 

 jugating elements to for7n '^ygosomes^ or 'mixochromosomes,' or 

 are they subsequently disjoined by a reduction division? Bon- 

 nevie ('06, '08) and Vejdovsky ('07) believe that parasynapsis 

 occurs and that in this process a complete fusion takes place, 

 which is permanent. As a result, a new chromosome is formed, 

 two longitudinal divisions occur, and a four-strand first-matura- 

 tion chromosome results. Both first and second maturation 

 divisions are simply equational, not reductional. Haecker 

 in his metasyndesis theory holds a somewhat similar view, with 

 this difference, however, that as a result of incomplete (only 

 half as numerous) transverse segmentations of a continuous 

 spireme, previously formed by the union end to end of the 

 chromosome threads, there appears just half the number of 

 segments (reduction), in which homologous spermatogonial 

 chromosomes find themselves united end to end. This union 

 is conceived to be permanent and evidence of it may be seen, 

 according to Haecker, in the transverse segmentation so often 

 visible in chromosomes of the copepods during both first and 

 second maturation divisions as well as in the division of soma 

 cells. Both niaturation divisions are, according to Haecker, 

 equational, merely dividing his two-part rods longitudinally 

 into four similar two-part rods to be distributed to the four sper- 

 matids. It will be seen that no reduction or segregation in the 

 usual sense of the term occurs. The germ cells, then, all receive 

 the same sort of chromosomes. 



In view of our work upon the transversely segmented chromo- 

 somes in Chorthippus and Jamaicana, whose segmentation we 

 have found to be due to the usually permanent association of 

 two non-homologous chromosomes, we have many reasons to 

 believe that Haecker has probably been dealing with similar 

 cases of compound chromosome formation. The work of Lerat 

 ('05), Matscheck ('10), Krimmel ('10) and others has shown the 

 presence in copepods of chromosomes in the form of V's with, 

 in many cases, unequal arms, as well as the usual segmented 

 copepod rod, which likewise in some figures has unequal instead 

 of equal segments. These observations agree with mine upon 



