STUDIES ON CHROMOSOMES 349 



mals (perhaps also in the Orthoptera) the conjugation is a side 

 by side union, or parasynapsis. On the other hand, the evidence 

 of a 'reduction-division' in the ordinary use of the term i.e., 

 the disjunction of the same chromosomes that unite in synapsis 

 seems to me to be far short of a demonstration. In these forms 

 synapsis is followed by a union so intimate that no adequate evi- 

 dence of duality can for a time be seen in the resulting bivalents. 

 I do not for this reason argue against the conception of the reduc- 

 tion-division. On the contrary, I shall offer new considerations 

 in favor of this conception in a somewhat modified form; but in 

 case of the autosomes it must for the present rest mainly upon 

 indirect evidence. In this respect the autosomes differ notably 

 from the sex-chromosomes, at least in the male sex; and this 

 difference may be of significance for some of the most interesting 

 phenomena of sex-heredity. 



in the course of which the apparent number of chromosomes is reduced to one-half. 

 "There are thus, after the rest of transformation, only one half as many chromo- 

 somes, i. e., separate chromatin-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 

 (from avva-irru, to fuse together) to denote the period at which this most impor- 

 tant change appears in the morphological character of reproductive cells" ('95, p. 

 287. In subsequent pages the phrase ' synaptic phase' is often shortened to 'synap- 

 sis' in the same sense). This 'most important change' is obviously the halving 

 of the number of chromosomes ; and nowhere in his paper is the word applied 

 to the contraction-figure, though the latter is stated to be "characteristic of this 

 particular phase in the spermatogo- and ovogenesis of a great variety of animal 

 forms" (p. 305). Though there was, perhaps, some obscurity in his original use of 

 the word, all doubt as to Moore's meaning is removed in a later paper, published 

 jointly with Farmer ('05), where synapsis is precisely denned as "that series of 

 events which are concerned in causing the temporary union in pairs of pre-maiotic 

 chromosomes" (p. 490). The fact that so many later writers have misapplied it 

 should not debar us from the continued use of so convenient and appropriate a 

 term one that seems particularly fitting if it be a fact, as a number of excellent 

 observers have concluded, that synapsis is followed by actual fusion. I can dis- 

 cover no reason why McClung's term 'synizesis' should not be generally employed 

 for the contraction-figure, as it already is by most American writers. 



