522 University of Calif ontia Publications in Zoology [Vol. li 



Figs. A to U. — Diagrams to illustrate possible modes of association in 

 synapsis of the fifty-six fine threads (leptotene) which are formed from 

 the nuclear network and become polarized with regard to the sphere which 

 lies at the proximal side of the nucleus. The large outer circle represents 

 the cell wall; the large inner, the nuclear membrane; the small one between 

 the two large, the sphere. 



Fig. A. — Of the fifty-six threads which are imagined as separate, dis- 

 tinct filaments eight are represented as forming two loops (amphitene) 

 by a double process of pairing. They form by parallel union four (of the 

 twenty-eight) Ys which by end to end junction give rise to the loops. 

 There is no evidence of such a condition. 



Fig. B. — Four complete threads are indicated, the eight ends of which, 

 corresponding to the eight separate threads of figure A, arise separately, 

 are at first merged into the nuclear network of the distal part of the 

 nucleus, and with the disappearance of the network become continuous 

 as four threads. These before completion and while potentialh^ present 

 in the network become paired in such a manner that the ends of two 

 threads unite to form two Ys, which by closing up give rise to a single 

 loop which is unconnected with the other. Fourteen such loops are formed. 



Fig. C. — The complete threads arise as in figure B. A different mode 

 of synapsis is represented in which the two ends of one complete thread 

 are not paired with the two ends of only o)ie other thread, but with one 

 end each of two other threads. 



Fig. v. — A later stage of the condition shown in figure C. showing 

 how with the final closing of the Ys the bends of the loops would be drawn 

 together, a condition not existing. 



