STUDY OF CHROMOSOMES OF LACHNOSTERNA. 89 



This unanalyzable stage is of relatively short duration and is 

 followed by a condensation of the chromatin in the form of heavy 

 threads (Fig. 25). Condensation of the chromatin continues 

 and the definitive maturation tetrads begin to make their appear- 

 ance. In these early prophases one often finds cells in which 

 all the chromatin is massed at one side of the nucleus (Fig. 26), 

 resembling very much a synezesis figure. Gross ('07) has 

 described a second synezesis in Pyrrhocoris and Mottier ( '07) be- 

 lieves that in the plants it is a regularly occurring phase in the 

 maturation processes. In Lachnosterna these contraction figures 

 are most abundant in material which is poorly fixed and I 

 consider them as artifacts. Fig. 27 represents this stage from 

 well fixed material as contrasted with Fig. 26 from poorly fixed 

 material. 



All the first spermatocyte metaphase plates of the four species 

 of Lachnosterna studied, as well as Pelidonota and Cotalpa, show 

 ten bivalent chromosomes the smallest of which represents the 

 sex pair (Figs. 8, 9, 10, n, 12). These are usually arranged in 

 characteristic groups with fine linin threads connecting the various 

 members of the complex to each other. A comparison of the 

 tetrads of L. delata with those of L. fusca (Figs. 28, 29) shows no 

 marked differences either in form or in size of the tetrads. Using 

 Miss Carothers' ('17) nomenclature, there are five atelomitic 

 tetrads (non-terminal spindle fiber attachments) and five telom- 

 itic tetrads (terminal spindle fiber attachments). The atelom- 

 itic tetrads are the largest in the complex and are derived from 

 the three pairs of J-shaped spermatogonial chromosomes and 

 two pairs of the bent rod-shaped ones. In sideview metaphases, 

 the largest of the tetrads (Figs. 28, 29) has a sub-terminal 

 spindle fiber attachment, and is derived from the AA pair 

 (Fig. 5) of the diploid chromosome group which also have sub- 

 terminal fiber attachments. The other atelomitic tetrads 

 consist of two typical crosses and two annular tetrads 'of the 

 Stenobothrus type. The other four autosome tetrads are of the 

 ordinary dumb-bell type while the x and y elements (sex pair) 

 are fused end to end (Figs. 28, 29) , 



The types of tetrads above described are found in all four 

 species of Lachnosterna studied. On the other hand, in Cotalpa 



