522 Theophilds s. Painter, 



it as an expression of internal stresses in the threads itself as it 

 eloiig'ates is not a matter of great importance. The essential thing 

 is that the leptotene-threads of the presynaptic period arise from 

 individual chromatin knots and the evidence would indicate tliat 

 these knots really represent the autosomes of the spermatogonia! 

 cells. The threads are segmented and the mode of origin would 

 indicate that they are present in approximately the same number 

 as the spermatogonia! autosomes. Actual counts are obviously 

 impossible. 



In the cells, shown in Figs. 26 and 27, we have leptotene stages. 

 Here, as in other similiar drawings, all the threads present in the 

 cell have not been represented. It has seemed wiser to draw what 

 could actually be seen rather than obscure these details by adding 

 the blurred outlines of the threads lying underneath. The indi- 

 vidual leptotene-threads are thin and have a fairly smooth outline 

 at this time. We do not find the peculiar knotted appearance of 

 the threads in Maevia vittata, such as characterises many other species 

 of spiders. No marked pairing of the leptotene-threads, just prior 

 to the synaptic contraction, has been observed. 



Accessory chromosomes and ctetosomes. 



During the leptotene period the accessory chromosome always 

 persists as a distinct densely-staining mass. It may appear as a 

 single nucleolus, or it may have the appearance of two rods lying 

 side by side. It has not been possible to follow the ctetosomes 

 through this period. 



Synizesis. The contraction of the leptotene-threads and the 

 pairing and fusion of these threads which follows, that is, synizesis, 

 seems to take place with extreme rapidity. The cells showing this 

 stage are rare in all of my preparations, although the leptotene 

 stage preceding and the pachytene stage following, are vei-y common. 

 Even after long extraction, it has not been possible to make out 

 any detail ol what was taking place at this time, in Fig. 28, we 

 liave a cell in which the chromatin is just beginning to go to one 

 side of the nucleus. It has not been possible in this cell or in any 

 other, to detect the least indication that a pairing was taking place 

 between the threads. The cell shown in Fig. 28 is of interest, as it 

 indicates the condition of the accessoiy chromosome at this time. 



A discussion of the question of synapsis will be taken up after 



