LTFK-OYOLE OF " GYSTOBTA" IRR.EC4ULAETS (^FINCH.). 43 



of the gametes (sporoblasts).^ Wlietlier tliere has been a 

 qualitative as Avell as a quantitative separation of nuclear 

 material, and how the selection has been brought about in the 

 absence of karyohiuesis, I am quite unable to say. 



The subsequent course of events in the two kinds is very 

 different. Fig. 49 a represents the least modified condition 

 of one of the somatic nuclei ; it differs chiefly from a germinal 

 one in having its chromatin aggregated in larger masses and 

 disposed more in the interior. At h, c, and (?, and in the large 

 nuclei in fig. 50, are seen further stages in the alteration. 

 The sterile nuclei do not at present divide any more, but grow 

 considerably, chiefly by an increase of nuclear sap ; at the same 

 time, there is an increase of the chromatoid granular matter 

 (cf. figs. 49 f^ and 50/>). 



Turning now to the smaller or germinal nuclei, I have no 

 doubt that division in these is henceforth indirect or mitotic. 

 Unfortunately, I could not see any divisions actually occur- 

 ring in these two preparations, as all the nuclei were in a 

 I'esting condition. Nevertheless, karyokinetic apparatus is 

 already quite distinct in connection with many of them, and at 

 a slightly later stage mitotic nuclear division is unmistakably 

 in evidence. At one oi- both ends of certain of the smaller 

 nuclei, and quite at the periphery,- is seen a little thickening 

 Avhich gradually assumes the form of a rounded grain. It 

 stains deeply with iron-ha?matoxylin, and is probably of 

 chromatic nature. From each of these bodies a few delicate 

 rays diverge into the surrounding* cytoplasm. The whole 

 structure is better developed later on, the central grain 

 especiall}^ becoming large and prominent (fig. 51 a and b). 



Nature and origin of the division centres. — I have 

 felt somewhat uncertain whether to regard these large con- 



1 It is interesting to note that Leger (22) lias also described an early dis- 

 tinction of the multiplying nuclei in Sty lorhynchus into sexual ones, ulti- 

 mately forming the nuclei of the gametes, and somatic ones, which are left 

 behind in the " somas " or cystal residue. 



- It is difficult to say whether the thickening is at first inside or outside the 

 membrane. - 



