CHROMOSOMES OF MOSQUITO 547 



separate from each other except in figures 9, 15, and 16 of 

 'metaphases' in which the homologues are in contact. This 

 'synapsis' as Metz calls it, I beUeve to be an artifact. 



c. SYNIZESIS 



The word synizesis was coined by McClung ('05) to denote a 

 "condition of the nucleus in which the chromatin is found massed 

 at one side of the vesicle, without regard to whether it is a 

 normal phenomenon or not." Synizesis is supposed usually to 

 take place at the beginning of the growth period. The word 

 synapsis has been used by many writers to denote this condition, 

 but it is clear that Moore ('95), who coined the latter term, 

 intended it to be used for the pairing of the chromosomes before 

 reduction. This will be treated more fully under Synapsis. 



The existence of synizesis, as a normal phenomenon, is ques- 

 tioned by many. In the case of the eggs of Paludina, however, 

 Popoff ('08) observed it, and concluded, as a result of his meas- 

 urements, that it is normal. There is no contraction of the 

 chromatin, but rather a rapid increase of the nucleus in size, 

 due to osmosis. This is not immediately compensated by ex- 

 pansion of the chromatin, and thus an appearance of synizesis 

 is produced. Much the same phenomenon was observed by 

 Lawson (MO) in plants and demonstrated by measurements. 



Stevens observed synizesis in Culex ('09) and states that "the 

 granular and beaded chromatin threads are wound about a 

 large nucleolus." She considers that it bears no relation to 

 synapsis but that it is a period of reconstruction. In Musca 

 domestica ('08), however, she states that it does not occur. 



Lomen ('14) is very skeptical of its being a normal phenomenon 

 since he obtained it with certain fixatives but not at all with 

 others. K-B-S-E, he states, gave it, but not S-A-E. 



Taylor ('14) seems to contradict herself in her statements 

 about synizesis. She considers that it marks off the spermato- 

 gonia from the first spermatocytes. When she finds it in very 

 young larvae she supposes that they are precocious in matura- 

 tion, but when she finds it in somatic cells (p. 391) she concludes 



