-I PERN1 MI.KAKY CHROMOSOMES, AND SVXAPSIS 



i\ < 1:1 i Hopmi.rs (sr 



N. M. STEVENS. 



'I'll' i ( '- i<!i:!>liilus which I have iist-d in this siudy, 



I ha\e ii"! liccii able to identify. The material s t -eiiis to be 

 homogeneous, .m<l i- the only species of this gemi- that I have 

 seen about Br\ n M.iur. The insects were found, usually in 

 pairs, in their bnrro\\s under stones, and wen- i < >llected in 

 < ><tober and November, i<m> and i<)ii. They are not abundant. 

 and onlv 7 m.di - \\ ured in 1910, and 5 in i<ii i . 



METHODS. 

 In ill- h individual a few aceto-carmine preparations 



\\ITC in. id. . .nid tin- rcniainder of the testes fixed in 

 mercuro-nitric iluid <>r in Remming's stronger (-liro 



'ic niixiiiM I In- \><-[ results were obtained t'rmn -i- ( |i..n< 

 "I I I* ininiii:' in.iit-ri.il. < ut 10/1 thick and stained \\ith thionin. 



^i 11 K\I \i i KAKV CHROMOSOMES. 



In one "i tin- I<H insects one, and in another \\\ -uprr- 

 A cliniin..-.!!!!!-- were found. Tlu-si- rhrunn -i >nn-- .ire 

 n.idilv di-iiii'<iii-ln-d li"in the other chromic-urn - b\- their 

 Miialh r -i/e ,unl i rralir brhavior. 



The -perm. no: 1 ' mia! chromosomes, like tho-e of Stenopelmatus, 



are diltn nil to count, because they do not form a llat jil.ite ,u 

 an\ stage, bin lie .it -oinewhat dilTerent K-\eU and o\eilap. 

 The number i-> probabk ,7, exclusive <M -upernuiiierai ; 



In the !ir-t -|>- i niatocytes there an i^ bi\alent- an<l the 

 uni\-.ilent A" 1-1 . \\lu-n no supernumeraries are preM-m Fig. i . 

 Fig. 2 -lio\\- i ^ bi\.iK-nts, the unpaired chronio^oiiu- A", and 2 

 -upernuiiu-rar-i The odd chromosome A' i^ u-uall\- found 



at one pole of tin- >pindle when the other chromosome-, are in 

 metapliase Fig ; r but it not infrequently lags behind the others 

 in the anapha-e 1 'ijr. 4) and is enclosed in a separate membrane 



219 



