1901.] NATUEAIi SCIENCES OF I'JIIEADELPHIA, 2G7 



before the latter stage. This is remarkable, since in all^'other 

 Hemiptera studied by me the chromatin nucleoli regularly"de- 

 crease somewhat in volume, generally to considerable degree, 

 before they take their position in the equator of the spindle. 



In Coriscus ferns Linn., the only other species of the Nabidce 

 studied, I found (preceding paper, ^.c. ) in the monaster stage of 

 the first maturation mitosis nine bivalent chromosomes and one bival- 

 ent chromatin nucleolus. In tlie growth period preceding there is 

 present in the nucleus one bivalent chromatin nucleolus of_large size 

 and a smaller one; but not a group of four bivalent chromatin nucle- 

 oli as in Nabis. If the chromatin nucleoli be regarded'as]^disap" 

 peariug chromosomes, for which view I have given reasons, then 

 we may conclude that Nobis annulatus, by virtue of showing four 

 of the chromatin elements on the Avay to disappearance, has 

 advanced beyond the stage of Coriscus fents. 



6. Corizus alternatus Say. 



Five testes of this species were studied. 



Only two clear cases of spermatogouic monasters were found 

 where all the chromatin elements could be readily counted; each 

 of these showed fourteen elements. As PI. X, fig. 18 shows, two 

 of the elements are rounded and much smaller than the others 

 (N. 2), and these are chromatin nucleoli. Of the twelve elongate 

 chromosomes proper, two (those marked A, fig. 18) are considerably 

 larger than the others; and one of these appears always to have 

 the form of a rod, while the other has a bent V-shape. All four- 

 teen elements are halved in the metakinesis. 



In the early portion of the growth j)eriod each spermatocytic 

 nucleus contains a clearly bipartite chromatin nucleolus, representing 

 a union of the two chromatin nucleoli derived from the sperma- 

 togonia; each of its univalent components appears occasionally 

 longitudinally split, which is unusual in the Hemiptera.^ In the 

 rest stage following (there is a complete rest stage in this species) 

 the nucleus (fig. 19) contains a bivalent chromatin nucleolus (N. 

 2), which has increased in volume and generally is ovoid in out- 

 line; but sometimes during the whole growth period the two 



'Dr. F. C. Paalmier, who has worked out the spermatogenesis of Anasa 

 iristis De G., has demonstrated to me a longitudinal splitting of the chro- 

 matin nucleolus in the growth period of the Lygaiid, Myodocha serripe» 

 Oliv. 



