152 The Scottish Naturalist. 



own peculiar species of the higher Algse from which they spring, and 

 into which alone they can develop. In the rder of Cyanophyceous 

 Algae species of Gloeocapsa are degraded by recent discoveries as sub- 

 ordinate forms of higher Cyanophyceous Algae, as Sirosip)hon, Oscil- 

 laria, &c. ; Gloeocapsa Itzigsohnii, Bornet, for example, was proved to 

 be a peculiar state*or development of &irosip>hon Bornettii, Zopf. 



11 Whilst no proof whatever has, as yet, been furnished for the vast 

 majority of the Cyanophyceae, as regards the genus Cylindrospermum 

 we will briefly characterize the interesting relation between a minute 

 Chroococcus and Gloeothece and a species of Cylindrospermum. The 

 filaments of this plant are composed of cylindrical or more or less 

 globular cells. The spores are much larger than the ordinary cells, 

 from which, at first, they are not readily distinguishable ; but, when 

 the frond has attained a certain age, the spore-cells begin to enlarge, 

 and, finally, assume a form and size apparently fixed ; the matured 

 spores are cylindrical, rounded at the ends, and surrounded with dis- 

 tinct yellowish coats. The relative position of spores and heterocysts 

 is various. The contents of the heterocyst are paler, the colour of the 

 cell-wall yellowish. The cell at first seems merely to elongate until 

 it reaches nearly twice its original length ; then the division commen- 

 ces. A median constriction divides the cells into two daughter-cells, 

 the filaments then assuming a moniliform aspect. The cells are 

 closely connected, no nuclei being discernible, as in JVostoc cells. 

 By this process the filament rapidly increases in length ; but at the 

 ends the new joint beco ne further separated until they are almost 

 detached. The separated cells remain together, and form irregular 

 masses, resembling Symckococcus. These changes were observed in 

 dried material, but were traced from uninjured filaments, and remind 

 us of the metamorphosis of Polypothrix amphibia, Zopf. Besides 

 these filaments we have seen many of Conferva-like appearance, 

 which are composed of cells three or four times as long as broad, 

 filaments with swollen yellowish cell-walls, and filaments composed 

 of thicker-coated cells. The cells of these filaments separate in a 

 similar manner to that before described. The result of the frag- 

 mentation (at the ends of the filaments) is a Chroococcus or Glosothece- 

 form. The Gloeothece-form springs from the Chroococcus-form, that is, 

 from the rounded cells by their repeated division." 



The remarks of, and case cited by, Schaarschmidt, aid a little, a 

 very little, in the development of this subject. It would have been 

 more satisfactory had his observations been founded on fresh material. 

 My own position in the matter is simply this : that, while heartily 

 sympathizing with those who hold that these low forms of vegetable 



