517 



the development of the tetrads, we can see that the long axis of this 

 period represents the long axis of the spireme stage and thus the 

 constriction at right angles to it represents the transverse division. 

 When the tetrad is drawn into the equatorial plate of the spindle this 

 transverse division lies in the plane of division and consequently the 

 first division must be interpreted as a reduction one. When the 

 daughter-dyads separate, they are clearly seen to be constricted in 

 the middle and this constriction is at right angles to the plane of the 

 first division and thus corresponds to the earlier longitudinal split. 

 In the second division the chromosomes are separated at this con- 

 striction and thus the second division is an equation division. Ob- 

 servations on two other species of the family Coreidsc; Euthoctha 

 galeator ¥ab. and Chariesterus antennator Fab, give similar results. 



Of the other forms examined, two belong to the same subfamily, 

 Pentatomiiii;e, as Pentatoma, on which Montgomery worked. These 

 two species were Euchistus variolarius Pal. Beauv. and Brochymena 

 arborea Say, and, while there is still a considerable gap which I have 

 so far been unable to fill, I have, I think, sufficient evidence to be 

 able to state that in these genera, though the process differs some- 

 what in detail from that in Anasa, there is ultimately formed a tetrad 

 equivalent to that in Anasa, and that here also one of the divisions 

 is a reducing, the other an equation division. 



The process in Euchistus is as follows. We find a segmented 

 spireme in which, in my preparations, there is a most clearly marked 

 longitudinal split (Fig. 9), similar to that in Anasa. These segments 

 elongate and the chromatin becomes more and more broken up (Fig. 10), 



Fig. 9. 



Fig. 10. 



Fig. 11. 



i 



Fig. 12. 



I 



until, as far as I have been able to find, all traces of definite bodies 

 apparently disappear. Judging however from the similar occurrences 

 in Anasa, this is apparent only, the structure being masked by the 

 diffuse condition of the chromatin. At all events we find in a latter 



