CYTOLOGY OF ANISOLABIS MARITIMA BON. 245 



In regard to the sex-chromosome of the forficulids, the author 

 would maintain that in Anisolabis we have neither unpaired 

 accessory chromosomes, nor a pair of unequal heterochromo- 

 somes, nor a pair of almost equal heterochromosomes, -as -pre- 

 viously described by various authors. The following conditions 

 are believed to exist : the female diploid number is 26, consisting 

 of 22 autosomes and 4 x-chromosomes ; the female haploid number 

 (inferred) is 13, consisting of 11 autosomes and 2 x-chromosomes; 

 the male diploid number is 25, consisting of 22 autosomes, 2 

 x-chromosomes, and a y-chromosome; half the second spermato- 

 cytes show 13 chromosomes, and the other half 12. The former 

 gives rise to two female determining spermatozoa, containing 

 11 autosomes and 2 x-chromosomes; the latter gives rise to 

 two male determining spermatozoa, with 11 autosomes and a 

 y-chromosome. 



It will be an interesting problem to see if the small mature 

 males, occasionally found in Anisolabis, are in some way related 

 to an upset in the normal chromosomal distribution described 

 above. 



8. SUMMARY 



1. The diploid number of chromosomes in Anisolabis is 26 

 in the female, and 25 in the male both in somatic and germinal 

 cells. 



2. The only variation from the above is in the male somatic 

 cells, where only 24 chromatic elements may often be counted. 

 This may be due to a fusion of the two x-chromosomes in the 

 male cells or to the loss of the y-chromosome. 



3. Primary spermatocytes show twelve chromosomes: eleven 

 are autosomal tetrads, and one an xxy-hexad. 



4. The xx-element together with 11 autosomal dyads pass 

 into one secondary spermatocyte; the y-element and 11 autosomal 

 dyads pass into the sister cell. 



5. In the interkinetic period the two x-chromosomes separate 

 and appear as discrete bodies in the second maturation spindle. 

 We therefore find 13 chromosomes in one half the metaphase 

 plates, and 12 chromosomes in the other half. 



