392 EDMUND B. WILSON 



1 . The question of synapsis 



The cytological problem of synapsis and reduction involves 

 four principal questions, as follows: (1) Is synapsis a fact? Do the 

 chromatin-elements actually cqnjugate or otherwise become asso- 

 ciated two by two? (2) Admitting the fact of synapsis, are the 

 conjugating elements chromosomes, and are they individually 

 identical with those of the last diploid or pre-meiotic division? 

 (3) Do they conjugate side by side (parasynapsis, parasyndesis), 

 end to end (telosynapsis, metasyndesis) or in both ways? (4) 

 Does synapsis lead to partial or complete fusion of the conjugating 

 elements to form 'zygosomes' or 'mixochromosomes,' or are they 

 subsequently disjoined by a ^reduction-division?' Upon these 

 questions depends our answer to a fifth and still more important 

 question, namely, (5) Can the Mendelian segregation of unit- 

 factors be explained by the phenomena of synapsis and reduction? 



Despite the prodigious accumulation of data regarding these 

 questions the unprejudiced student of the literature finds himself 

 compelled to admit that not one of them has yet received a really 

 demonstrative answer — at least not one that has brought convic- 

 tion to the minds of all competent cytologists. I do not propose 

 to consider them exhaustivel}^, or to give any approach to a com- 

 plete review of the literature. This has been done by other writ- 

 ers, notably by Gr^goire ('05, '10) in two extended and masterly 

 memoirs, by Strasburger in a most valuable series of critical 

 essays ('07, '08, '09, '10), and by Haecker ('07, '10). (See also 

 Davis, '08, Gerard, '09, Gates, '11, Montgomery, '11, and the 

 series of papers by the Schreiners and by Janssens.) I will 

 however indicate some of the conclusions to which I have been 

 led in an effort to form an independent judgment concerning the 

 facts, especially in Tomopteris and Batracoseps, which are prob- 

 ably unsurpassed as objects of observation, have become classi- 

 cal through the well known studies of the Schreiners ('06, '08) 

 and of Janssens ('03, '05), and have formed a main center of con- 

 troversy in recent years. 



The conclusions of these observers (more especially those of the 

 Schreiners) have been the object of repeated criticism on the part 

 of Goldschmidt ('06, '08), Fick ('07, '08), Meves ('07, '08, '11), 

 Haecker ('07, '10) and many others. These criticisms, too well 



