CHROMOSOMES IN COREID HEMIPTERA. SQ 



2. Anas a tristis. 



The spermatogonial groups have been figured by Wilson ('056 

 and '061, and the number of chromosomes stated as 21. Wilson's 

 count ha- been corroborated by Montgomery ('06) and by Le- 

 fevre and M<< ,ill ('08) though Paulmier ('99) and Montgomery 

 in .in earlier paper ('01) had given the number as 22. Foot and 

 Sirol-ell 07-.' .UK! 076) have disputed the twenty-one count and, 

 on i In- li.i-i- D| photographs of smear preparations, have concluded 

 thai tin- iminb'-r is 22, confirming Paulmier's original account. 

 A r<< \aininatioM of fresh material from two different localities 

 ga\e j i a- il:' correct number of spermatogonial chromosomes 

 in a-niineiit \\ith accounts of Wilson, Montgomery, and of 

 l.i !( \i. and M< ('.ill. Imperfect plates it is true may show less 

 i ban ilii- inimU-r, but none were found with more. In Chelinidca 

 I'itti'j.i-ni, \\lnn- the spermatogonial groups are aln ost identical 

 \\itli tho-r o| Anasa, a single exception may be cited, in which 

 22 > In were foil nil. Apart from this, all clear plates 



. j i . 



A- poinieii out l>\ Wilson and by Lefevre and Mc(iill, the 

 -pi mi il groups of Anasa show two m-chromosoraes and 



three ! chromosomes one of which must be the unpain-d 



chromosome heterotropic" or "accessory" chromosome) though 

 ii cannot be precisely identified by its size or shape. Fig. 3, c 

 and :'. -li"u- tuo spermatogonial groups illustrating these points. 

 o-^oiiial groups (Fig. 3, a and b) contain 22 chromosomes, 

 iiu lining two m-chromosomes and four largest chromosomes. 

 (>t the la-i named, two must be the idiochromosome pair, cor- 

 "ii.lin- to du- unpaired idiochromosome of the spermato^oui.i, 

 as poinied out b> Wilson in the third of his "Studies" ('06). 



The nieiapliase of the first oocyte division was found in eggs 



taken troiii i he lower part of the oviduct. Fig. 3, e,f, g and //, 



-liou- toni Mich phases, /; being a composite figure from two 



There are ii chromosomes in each, all undoubtedly 



- i he in size between the chromosomes as a whole of Fig. 3, < ami /. 



.in, I tha . and It. is probably due to a difference in the length of fixation. 



In tin- formi ie eggs were left for ten minutes in the fixative (alcohol-acetic- 



-iil.liiii.il. in i la latt.-r. for five minutes. The chromosomes of Fig. 3, g and /;, 



-h,.u tin- -u riling action of the acetic unchecked by the sublimate which 



pen< 



