242 WM. REES B. ROBERTSON 



from the 'bouquet' up to the metaphase was wrong. His mis- 

 take has caused no Uttle confusion in the work of younger 

 investigators. 



With the exception of the workers on copepod material, and 

 of Agar (Lepidosiren) , no one thus far cited has shown in 

 the first maturation chromosomes resulting from V-type pairs 

 segmentation at the apices of the separating halves of the per- 

 pendicular rings, such as may be seen in figures 174 to 183 of 

 Chorthippus. In Lepidosiren Agar ('11, figs. 27, 28, 30; '12, 

 fig. 13b and c) has illustrated this segmentation in his perpendic- 

 ular rings of the 'j/ 'k,' and 7,' stages. The V's of Lepidosiren 

 have such short arms, however, that there results from them 

 (when all parts of the pair of V's except the extreme distal ends 

 have gone through the disjoining process) a four-part ring-tet- 

 rad, similar to what vom Rath described for Gryllotalpa. We 

 can now understand the peculiar figures which vom Rath gave, 

 for Payne ('12) has shown that in Gryllotalpa there are many V's. 



2. Is there pre-reduction or post-reduction in autosome tetrads? 



In a former paper (Robertson, '08, on Syrbula admirabilis) 

 I held that an end-to-end synapsis of homologous chromosomes 

 took place, that the first spermatocyte division was a longitudi- 

 nal division of each of the conjugating members of a pair, and 

 that the second division was the true reduction division. In 

 that work, so far as the actual observations are concerned, I 

 was correct and the observations will stand. My interpreta- 

 tion of the results, however, was incorrect. 



In the first place, I did not make a study of the early stages of 

 the spermatocyte, where parasynapsis has been found to take 

 place. My conclusions in favor of telosynapsis were based, I 

 now find, upon what is really the end stage of parasynapsis. 

 I have been forced to the present position by the study of the 

 V-chromosomes in Chorthippus in comparison with those of 

 Syrbula acuticornis. The first spermatocyte metaphase (figs. 

 179, 180) of Chorthippus shows in the compound chromosomes 

 the 7 and 11, the 5 and 9, and the 8 and 10 parts behaving so 

 much like the same (but independent) tetrads in Syrbula (figs. 



