OF THE GERM CELLS OF METAZOA. 203 



and chromosomes in the rest stage are green, the true nucleoli red ; with Delafield's 

 hgematoxylin and eosin, the chromatiu. imcleoli and chroinosoines stain blue, the true 

 nucleolus red ; with both these methods the chromatin nucleoli stain more intensely 

 than the chromosomes in the rest stage. 



In the spermatogonia the chromatin nucleoli are generally small, often very minute 

 and difficult to distinguish. They are apparently always halved in the spermatogonic 

 mitoses, though I have not been able to determine this for all species. They always 

 increase in volume during the growth period of the spermatocytes ; the relative amount 

 of this increase varies in different species, but it is a number of times greater than in the 

 spermatogonia. During this increase in mass there can be found in most cases a clear 

 vacuole in the chromatin nucleolus, so that the increase would appear to be not so much 

 one of the proper substance of the chromatin nucleolus as of an intussusception of fluid 

 from without ; I have not figured these vacuoles in the present paper, but showed them 

 in a preceding one (1898 a). In the prophases of the first maturation division the 

 chromatin nucleolus decreases very considerably in volume, until when the monaster 

 stage is reached its volume may be very little greater than in the spermatogonia. It is 

 possible that its increase in mass during the growth period may be due in part to a decon- 

 densation of its substance, but in some part at least it is due to the above-described 

 taking in of fluid substance from without. 



In the spermatogonia they are irregular in position, sometimes close together, some- 

 times separated, but usually not in contact with the nuclear membrane ; in these cells 

 they are very frequently in all species apposed to the true nucleoli.* In the growth 

 period of the spermatocytes they are more regular in position : thus they are separated 

 from the true nucleoli and then always in contact with the nuclear membrane in 

 Euchistus, Mormidia, Peribalus, Cosmopepla, Nezara, Brochymena, Trichopepla, Eury- 

 gaster, Metapodius, Anasa, Chariestents (generally), Corizus, Harmostes, Calocoris, Hygo- 

 trechus, Limnotrechus ; they are, as a rule, apposed to the true nucleoli in Podisus, 

 Perillus, Ccenns, Alydm, Protenor, Peliopelta (not always), (Edancala, Oncopeltus (not 

 always), Leptoptema, Pcecilocapsus, Phymata, Coriscus, the Reduviidce, Limnobates and 

 Zultha. We shall refer again to the significance of this apposition. A chromatin 

 nucleolus and a true nucleolus closely attached together constitute a " double nucleolus ;" 

 it remains to be shown whether the " double nucleoli " of certain cells of other Metazoa, 

 as e. g. in the cells of Sertoli of Salamandra and Mus, as described by Hermann and 

 others, may also be cases of apposed chromatin nucleoli and true nucleoli. It is very 

 characteristic of the chromatin nucleoli of the spermatocytes in the growth period to be 

 closely apposed to the nuclear membrane. And when they are apposed to true nucleoli, 



* In the spermatogonia there are in all species an irregular number of true nucleoli, but in the spermatocytes of 

 most of the species examined there is regularly one large one. 



