BEHAVIOR OF NUCLEUS AND CHROMOSOMES. 159 



In the other Diptera known to us, 1 conditions are not usually 

 such as to reveal the presence of a chromosomal envelope if one 

 its. But indications of one are to be seen here and there, 

 --penally in late prophases or metaphases. And in one genus, 

 owing to the unusual nuclear behavior somewhat like that in 

 I.-! ij)ogon the evidence is strong. This genus is Ptecticus, a 

 number of the Stratiomyidie. It will be considered more fully in 

 another paper, but we may note here that in P. trivittatits and 

 P. sackenii, the two species we have studied, there is a distinct 

 hyaline zone around the chromosomes of the prophase and meta- 

 ph.ise of the spermatocyte divisions, and there are indications of 

 such a structure extending back into the growth period. These 

 ures are shown in part by Figs. 14 and 15, from prim.iry 

 spermatocytes of P. trivitlatns. 



This condition, in a family distinct from that to which Lasi- 

 '>n belongs, suggests that we are dealing with something which 

 is widespread at least among the Diptera. 



In other organisms the nearest approach to conditions like 

 those described above, so far as we are aware, is found in the 

 Orthoptera. Professor Mc(Mung informs us that in this group 

 prophase and metaphasc chromosomes (of primary spermato- 

 cytes) are frequently bordered by clear spaces, differentiated 

 from the surrounding cytoplasm, and that the condition is suffi- 

 ciently characteristic to suggest the constant presence of a 

 hyaline zone around the chromosomes in these stages. As 

 examples may be cited McClung's published photographs of the 

 in-t spermatocyte chromosomes of Mermeria (Mr('hmg, '14, 

 I igs. 129-132) and of Ilesperotettix (McClung '17, plate 8, I 

 c}. In all of these the hyaline zone is visible around the chro- 

 mosomes. 2 We have observed this condition in fn-t -pcrmato- 

 i-yte anaphases of Rhomaleitm and find that the hyaline l.i\-r 

 agrees in appearance with that in Lasiopogon, alt hough we have 

 not as yet tried to trace its history. 



The presence of this condition in the < )rthopu-r.i .md I )ij>tera 

 It. i- prompted us to make a brief comparison with other structures 

 of a somewhat similar nature. 



No close relatives of Lasiopogon have been examim-il a- y-t. 

 - It is probable that other cases of this sort have escaped our notice, although we 

 li.ive examined numerous published photographs of chromosomes with ttiis point in 

 mind. 



