80 ETHEL NICHOLSON BROWNE 



may be afforded in two ways; by a flow along the whole length of 

 the spireme and (for a brief period) by the connection of the curves 

 of the loops with the karyosphere. After the loops become dis- 

 connected and oriented, they give somewhat the appearance 

 of the 'bouquet/ though this is never so regular or clearly marked 

 as in Batrachoseps, Tomopteris, etc. The polarized loops of 

 the bouquet stage are in other forms the forerunners of the chro- 

 mosomes. This may also be the case in Notonecta, but if this 

 be so, the conclusion seems unavoidable that the fundamental 

 material must subsequently return to the karyosphere, for, as will 

 be shown,, the chromosomes later arise directly from the latter. 

 It is possible that this material flows back into the karyosphere 

 along the faintly staining threads that can usually be traced from 

 the loops; but it seems more probable that after the loops are 

 disconnected, their substance does not enter the karyosphere. 

 This conclusion is based on the fact that the loops withdraw from 

 the karyosphere, and that some of the more remote threads keep 

 the chromatin stain after the ones near the karyosphere have lost 

 it. If this be so, considerable ground is given for the view that 

 there are here two kinds of chromatin, corresponding with those 

 designated by Lubosch ('02) as trophochromatin and idiochro- 

 matin. The chromatin, which is later to form the chromosomes 

 is transferred to the karyosphere in one or both of the two ways 

 suggested, while the rest of the chromatin becomes disconnected 

 from the karyosphere and is represented by the flaky reticulum 

 in the nuclear cavity.'' In the case of N. glauca, Pantel and 

 Sinety have likewise concluded that the material in their ' monili- 

 form cords' becomes achromatic and is spread through the nuclear 

 cavity, taking no part in the chromosome formation. This ma- 

 terial has no doubt a metabolic function during the enormous 

 growth of the spermatocyte. From a comparison of figures 51 and 

 53 drawn to the same scale, it is evident that the surface of an 

 equatorial plane of the full grown spermatocyte nucleus is approx- 

 imately five times that of the youngest one, which means that its 



^ The paper of Vejdovsky ('12), containing very interesting observations, bear- 

 ing on this and other subjects here treated, unfortunately came to my notice too 

 late for his results to be incorporated in this article. 



