CHROMOSOMES OF MOSQUITO 555 



important phenomenon of this period. It is merely 'diagnostic.' 

 That the numerical reduction of the chromosomes is the essen- 

 tial feature appears from page 287. "There are thus, after the 

 rest of transformation, only half as many chromosomes, i.e., 

 separate chz'omatic masses, as there were before, and the halving 

 of their number, being brought about while the nuclei are still 

 at rest, is to that extent comparable to what is now known to 

 go forward during the maturation of the reproductive elements 

 of plants. I therefore propose the term Synaptic phase to denote 

 the period at which this most important change appears in the 

 morphological character of reproductive cells." 



Again, in 1905, Farmer and- Moore, consider the question 

 of reduction. The term synapsis is derived from the Greek 

 avvoLiTTHu, to fuse together, and is used to refer to the union of 

 the homologous chromosomes rather than to the contraction of 

 the entire chromatin content. "The synapsis represents that 

 series of events which is concerned in causing the temporary 

 union in pairs of pre-maiotic chromosomes, previously to their 

 transverse separation and distribution, in their entirety, between 

 two daughter nuclei." Synapsis takes place then in the first 

 gametocyte nucleus, in the rest of transformation. 



The terms 'maiosis' or 'maiotic phase/ from the Greek /zeicotm, 

 reduction, are used "to cover the whole series of nuclear changes 

 included in the two divisions that were designated as Hetero- 

 type and Homotype by Flemming." 



. Farmer and Moore subscribe to telosynapsis and prereduc- 

 tion. In discussing the spermatogenesis of an Acridian, Wen- 

 rich ('16) demonstrates parasynapsis and reviews the work of 

 other investigators upon other forms. In the Acridian the 

 chromosomes enter the synaptic period as single leptotene 

 threads. The homologues conjugate parasynaptically during 

 the zygotene stage, and at the end of the growth period a sec- 

 ondary split at right angles to the original plane of separation 

 becomes evident. Four chromatids are thus demonstrated which 

 are the four elements of the tetrad. 



It would seem in general, from the more recent work, that 

 parasynapsis is at least the more usual mode of pseudoreduction 



