180 MONTGOMERY A STUDY OF THE CHROMOSOMES 



bipartite in the growth period (Fig. 165) ; and (4) the fact that they remain separate 

 from one another in the first maturation division, and that each divides transversely 

 (Figs. 167, 169, 170, N. #). The last mentioned point deserves particular consideration, 

 for a transverse division of a chromatin element in the Hemipto-a always means a reduc- 

 tion division /. e., a separation of two whole nnivalent components of one already biva- 

 lent element. From these facts we are led to the conclusion that here the chromatin nu- 

 cleoli are virtually bivalent in the spermatogonia, and that since the spermatogonic division 

 gives a longitudinal half of each of them to the spermatocytes, that each is already 

 bivalent in the spermatocytes & bivalence then produced before the synapsis stage of 

 the growth period. This conclusion would explain all their peculiarities listed above. 

 In the spermatogonium accordingly there would be virtually four chromatin nucleoli, 

 twice the number found in the other species of the Lygci'ldce (with possibly the exception 

 of the not fully explained Ichnodemus falicus). 



CAPSIDJE. 



/ 



28. Leptopterna dolabrata Linn. 



Three testes of this species were studied. 



There were no spermatogonia on any preparations (taken from adults in the last in- 

 star before copulation). 



In the rest stage of the growth period of the spermatocytes are found the following 

 relations for the chromatin nucleoli : There are two chromatin nucleoli, which (1) are 

 attached to one another but separate from the true nucleolus (Plate IV, Fig. 172) ; (2) 

 they are attached together and to the true nucleolus (Fig. 173) ; (3) they are separated 

 from one another but both attached to the true nucleolus (Fig. 175), often at opposite 

 poles of the latter (Fig. 174). In almost all cases they are attached to the true nucleolus, so 

 that Fig. 172 represents an unusual case. Each chromatin nucleolus is probably a nniva- 

 lent one, for it never shows a bipartite appearance and is usually rounded, so that in Figs. 

 172 and 173 the two together would constitute one bivalent chromatin one ; but there 

 cannot be certainty on this point until the number in the spermatogonia is determined. 



Pole views of the monaster stage of the first maturation division (Fig. 176) show 

 seventeen chromatin elements, one of which, centrally placed, is always much larger than 

 the others. On lateral view all appear dumbbell-shaped and so are probably biva- 

 lent. Probably one of these elements represents the bivalent chromatin nucleolus de- 

 scribed for the growth period, then the sixteen remaining would be chromosomes. 



