CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIPTERA HETEROPTERA. 141 



maturation mitosis red actional ly and in the second equationally ; and one monosome, 

 much larger than tlie bivalent diplosoine, always compact in the growth period (ex- 

 cept in (Edancala, and in Harmosfes it may become more or less reticular), which divides 

 equationally in the first maturation mitosis, but does not divide in the second. This 

 condition was first described by me for Protenor and CEdanmla, then found by Wilson 

 for Anasa, Alydics and Harmostes, and in the present paper it is described for these 

 genera as Avell as for Corizus, Chariesterns and Mektpodius. Accordingly, Sijromastes 

 would appear to be the only Coreid thus far described which does not conform to this 

 type. 



C2. In G'docoris there are two bivalent diplosomos tliat divi<le in tlie maturation 

 mitoses first reductionally and tlien equationally ; a smaller monosome that does not 

 divide in tlie first maturation mitosis, but does divide in the second ; and a larger 

 monosome that divides in tlie reverse order of this. The monosomes remain compact 

 during the growth period, but the diplosomes do not. 



C3. In Lygus there is a single, very small monosome that does not divide in either 

 maturation mitosis. And one pair of diplosomes of very unequal volume, which 

 divide separately and equationally in the first maturation mitosis, conjugate in the 

 second spermatocytes and divide reductionally. Another bivalent element, the smallest, 

 which divides like the autosomes, may be another diplosome pair, but this could not 

 be distinctly determined l)y me. 



CI. In Archimerm Wilson ( IQOoc) finds that the monosome does not divide in 

 the first maturation mitosis, but in the second divides equationally ; while a, l)ivalent 

 diplosome with small components of equal volume divides first reductionall}' and 

 second equationally. 



C4. And in Baiiasa Wilson (1905c) describes a monosome that behaves like that 

 of Archimerus, together with a pair of ver}' unequal diplosomes that divide in the 

 first maturation mitosis separatel}^ and equationally, conjugate in the second sperma- 

 tocytes, and then divide reductionally. 



The other groups where allosomes are known to occur are the following. In the 

 spermatogenesis of the Orthoptera according to the researches of Wilcox (1895), 

 McClung (1899-1905), Sutton (1900, 1902?;), de Sinety (1901), and Baumgartner (1904) 

 there is a single monosome said not to divide in the first maturation mitosis but to 

 livide equationally in the second. The only exceptions among tlie Orthoptera are 

 Sijrhula, where I showed (]r05) there to be a pair of diplosomes which conjugate early 

 in the growth period, and divide first reductionally and then equationally in the 

 maturation mitoses ; Hippiscus as described by McClung (1900), where a single mono- 

 some is stated to divide in Ixjth maturation divisions ; Stenopelmatus, where Miss Stevens 



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