ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 407 



upon it as an equatorial band. This band is homologous with the disk 

 seen in living material. As the disk evolves, chromatic bodies, averaging 

 fourteen for this species, are to he seen on the band, while other irregular 

 masses of chromatic material project as loops or pyramidal masses from 

 its edge. These loops or masses represent material from nuclear 

 plasm and central body that has partially amalgamated. 4. No rift 

 appears in the living disk to indicate a sharp splitting of components, 

 1)ut instead the changes in appearance indicate a thinning in the centre, 

 while parts reassemble at either pole. The chromatic bodies in the 

 fixed disks appear as viscous masses that, as they amalgamate, elongate, 

 while other disconnected chromatic masses are discharged into the 

 cytoplasm as the disk separates into the halves passing to the poles. 

 ."). The living disks may be seen sometimes to pass e/i masse to the poles, 

 but more usually they divide their substance into a few continuous 

 strands, to reassemble as disks at the poles of the anaphase. These 

 strands cannot be identified as moving chromosomes, since no units can 

 be discerned in them. As the disks approach the poles, they appear to 

 blend with similar disks apparently evolved from cytoplasm. 6. Each 

 daughter-disk thus arising upon fixation consists of a series of about 

 four rows of tetrahedral masses. In living material the same appears 

 as a translucent rim surrounding a less dense interior. The translucent 

 rim becomes the nuclear plasm, while the central body takes shape 

 within the less dense interior. 7. Spiroffyra, as exemplified in S. hellis 

 and S. crassa, may be characterized as having chromatic substance of 

 a polymorphous nature; in the one a disk, in the other a spireme. Tlie 

 nucleolus does not fragment directly into chromosomes, as upheld by so 

 many investigators, but only contributes the less dense substance seen 

 at metaphase, which eventually may be discharged or become partially 

 amalgamated with the chromatin. Hence Spirogtjra, as regards the 

 constitution and behaviour of its nucleolus, need not be placed in a 

 different category from the remainder of the green alga3 or from that 

 of higher plants. 



New Genus of Siphonese.* — F. v. Wettstein found in November, on 

 the ploughed land of a cabbage field near Kremsmiinster, a colourless 

 species pf Siphonete, which was harbouring within itself a Nostoc. The 

 plant was rare, and was only found in one other neighbouring field. 

 All attempts at culture proved a failure. Each individual consists of 

 a large number of pear-shaped vesicles, bound together by a much 

 branched mass of rhizoids, among which can be distinguished one or 

 several main rhizoids. The lateral rhizoids either throw out vesicles 

 or they penetrate into the ground and develop into much-branched 

 filaments, thus serving as holdfasts and as organs of nutrition. Nowhere 

 were any transverse septa found. The rhizoids are quite full of proto- 

 plasm, but on the walls of the vesicles there is only a thin layer. Every- 

 where in the protoplasm are the small typical Siphonete-nuclei. Oil- 

 drops occurred throughout the plant. No chromatophores were present. 

 The relatively thick, distinctly stratified membrane consists of chitin, 



* Oesterr. Bot. Zeitschr., 1915, pp. 145-56 (2 pis.). See also Bot. Centralbl., 

 csxxi. (1916) pp. 131-2. 



