394 EDMUND B. WILSON 



hervorgerufen kann, namlich erstens eines mehr zufalligen oder, besser 

 gesagt, selbsverstdndlichen teilweisen Parallelismus der Fdden, wie er 

 durch die in der Synapsisphase bestehende polar e Anordnung derKern- 

 substanzen bedingt wird, und zweitens einer verfriihten, bei den ein- 

 zelnen Objekten und Individuen je nach dem physiologischen und Kon- 

 servierungszustand bald friiher, bald spater, bald regelmassiger auf tre- 

 tenden primaren Ldngsspaltung ('10, p. 185). 



Without citing other zoological critics at this point, attention 

 may be called to the increasing tendency now apparent among 

 botanical cytologists to reject, or at least to restrict, the theory 

 of parasynapsis held by Strasburger, Allen, Berghs, Gregoire and 

 a large number of other botanical '' zygotenists/ in favor of a telo- 

 synaptic conception like that of Farmer and Moore('05), itself 

 essentially like that many years earlier maintained by Haeckerand 

 Riickert among zoologists. Among these may be mentioned 

 Mottier ('07, '08), Gates ('08, '11), Davis ('09, '11) and Digby 

 ('10). These observers and others, though differing more or 

 less as to the details, are in agreement on the essential point 

 that in some species at least the synaptic connection of the 

 chromosomes is end to end, not side by side; and that a longitu- 

 dinal duality of the spireme-threads at the synaptic period 

 (synizesis, or earlier) is either absent, or if present is due either 

 to an accidental parallelism or to a longitudinal splitting compara- 

 ble to that seen in the diploid prophases. These observers are 

 in substantial agreement that the chromosomes (if persistent 

 entities) are originally arranged in linear series, and united end 

 to end, in a spireme-thread which ultimately breaks apart into 

 bivalent segments, each consisting of two chromosomes in para- 

 synaptic union. The sidewise pairing, which undoubtedly occurs 

 in some plants, is believed by Farmer and Moore, Mottier, and 

 others to result from a secondary looping of these segments, which 

 takes place long after the synizesis stage. Gates, however, 

 expressly adopts the view that synapsis may take place by either 

 method in different species, possibly even in the same species. 



I must admit that my own faith in parasynapsis (such as it 

 was) and even in synapsis itself, was materially shaken by some 

 of the criticisms and observations that have just been indicated, 

 and that I took up the study of the question in a distinctly scepti- 



