Studies on Chromosomes 159 



latter case appearing dumb-bell shaped as seen in polar view. 

 The eccentric idiochromosome is of nearly the same size as the 

 smallest of the large bivalents and is often indistinguishable from 

 the latter except by its position. All these chromosomes divide 

 equally in this division, the m-chromosomes usually leading the 

 way in the march towards the poles, while the idiochromosomes 

 often lag slightly behind the others. 



The second division likewise shows 11 chromosomes in polar 

 view (3, c, d)\ but the regular grouping characteristic of the first 

 division is now usually lost, the ring formation being often no 

 longer apparent, while either the w-chromosome or the idiochro- 

 mosome may now occupy any position.* In this mitosis all the 

 chromosomes divide except the idiochromosome which lags behind 

 the others and finally passes undivided to one pole (Fig. 3, e-h, 

 Photos 14, 15) as Montgomery described. The nucleus formed 

 at this pole thus receives 11 chromosomes, the sister nucleus but 

 10, precisely as in Anasa, Narnia, Chelinidea or Leptoglossus. 

 This is proved beyond all doubt by polar views of the anaphases, 

 showing the sister groups lying one above the other in the same 

 section (Fig. 3, h). In the particular example figured the idio- 

 chromosome lies eccentrically, but this is quite inconstant. 



The spermatogonia (Fig. 3, /, /) always show 21 chromosomes, 

 a largest and a smallest pair being always distinguishable. The 

 unpaired idiochromosome cannot be distinguished from the others. 

 The m-chromosomes are usually equal, but sometimes appear 

 slightly unequal. 



In the growth-period the m-chromosomes and the idiochromo- 

 some have the same history as in other coreids. The former are 



* The regrouping of the chromosomes in the second division, first described by Pauhnier ('99) in 

 Anasa tristis, is characteristic of the Coreidae generally, an eccentric position of the idiochromosome 

 being a nearly constant feature of the first division but not of the second. Failure to recognize this 

 fact in the case of Anasa tristis seems to have been one of the main sources of error in the entirely mis- 

 taken conclusions of Foot and Strobell ('07a, '07b) regarding this species. (Cf. Lefevre and McGill, '08.) 

 Demonstrative evidence on this point is given by polar views of rather late anaphases in which every 

 chromosome of each daughter plate may be seen in the same section. Such views, of which I have 

 studied many, both in Anasa and in other genera, show that oneof the chromosomes may indeed occupy 

 an eccentric position, and may there divide; but in such cases the odd chromosome is always found 

 elsewhere in the group, lying either in or near one of the daughter-groups and not in the other. When 

 the odd chromosome is eccentric it is found in one of the daughter groups but not in the other. 



