I2O FERNANDUS PAYNE. 



the small idiochromosome produces males and the other class 

 females. Wilson likewise established the fact that in forms 

 having an accessory chromosome, the spermatozoa that contain 

 this chromosome are female-producing, the others male-produc- 

 ing. In respect to sex-production, the accessory chromosome is, 

 therefore, identical with the large idiochromosome. The homo- 

 logue of the small idiochromosome is lacking. 



The relation of the accessory chromosome to sex-production 

 has been confirmed by the work of Montgomery ('06) on the 

 Hemiptera heteroptera, of Stevens ('05 and '06) in the Coleop- 

 tera, of Boring ('07) on the Hemiptera homoptera, of Lefevre 

 and McGill ('08) on Anasa and Ana.v (one of the Odonata), and 

 of Wassilieff ('07) on the cockroach. It has also received con- 

 firmation in the recent work of Morgan ('08) and von Baehr 

 ('08) in the parthenogenetic reproduction of Phylloxera and 

 Aphis. 



Wilson ('09) has described a third type in Syromastes. Gross 

 ('04) showed that the accessory chromosome in this species is 

 bivalent, but described and figured 22 chromosomes in both male 

 and female cells. Wilson confirmed this for the male, but in- 

 ferred that the female cells should contain 24 chromosomes or two 

 more than the male, and he has since confirmed the correctness 

 of this inference by direct observation. Hence, contrary to the 

 assumption of Gross, both classes of spermatozoa must be func- 

 tional, the class containing the bivalent accessory chromosome 

 producing females, the others, males. 



A fourth type was described by myself ('08) in a preliminary 

 note on Gelastocoris (Galgnlus). In this type there are five 

 chromosomes which divide as univalents in the first maturation 

 division. In the second division they do not divide, but four 

 of the five pass to one pole and the other one to the opposite pole. 

 In this form the female has three more chromosomes than the 

 male, and the spermatozoa which contain the three extra chromo- 

 somes must therefore be the female-producing class. 



A study of the Reduviidas has brought to light several addi- 

 tional types here to be described. In Diplocodus, belonging to 

 this family, occurs the second type with one large and one small 

 idiochromosome. As in Lygceus and other forms, these divide 



