*iOS Frit8cli. Studies on tVanopliyceae. 



lower cells of the filamcnt, tliose sitnated more apieally having lost 

 tliis power witli ihoir tondency to develop into hair-ceUs. This 

 difforeiiliation of apex and base of tlio filamont, whicli tliiis also 

 finds its ('X])r('Ssion in the external sheatli and is of course like- 

 Avise exhil)ited by tlie strictly basal development of the ssingle 

 large spore, is also noticeabl«' in reference to the immediate 

 Investments of the cell. In the basal cells of a lilament the 

 cell-sheath is readily visible oiitside the colourless inner invest- 

 ment of each protoplast (fig. 10, c. s.j: in most hlanients it is 

 however less and less easy to recognise as one advances towards 

 the apex and the cells, which make up the hair-like termination 

 of the filament, are invariably devoid of a cell-sheath and only 

 possess the inner investment. As in the case of the external 

 sheath, mentioned ubove, is is ver}^ diflicult to fix the precise 

 point, at which the cell-sheath is no longer evident, nor is this 

 point by any means constant in different hlaments; in one case 

 the greater nuniber of cells of a filament are without the cell- 

 sheath, whilst in another the majority is provided with this 

 latter investment. The cell-sheath presents the same marked 

 nioniliform structure, as in the filanients of a TohjpotJirix and 

 for whole Stretches the cell-sheaths of the individual cells may 

 be quite distinct from one another, as in Aiiahaona-^ in such 

 regions the structure of the filament is identically that of this 

 latter genus. On the whole however the cell-sheaths are more 

 commonly found united, although such a coherent cell-sheath 

 differs from that of OscUlaria and agrees with that of a ToJij- 

 pothrix. in its very marked nioniliform constrictions. 



The Single large basal spore develops from a singie vege- 

 tative cell by great increase of size of the latter; as develop- 

 ment proceeds the external mucilage at the base of the filament, 

 becomes more and more distinct, and ultimately forms a rather 

 closely-fitting sheath round the mature spore. It is noticeable 

 that, whereas the ordinary vegetative cells are only stained 

 faintly brow^n by lodine, the sporogenous cell and offen also 

 one or two of the foUowing cells take on a deep brown colour. 

 I hojie to be able to furnish fm'ther dotails of the development 

 of the spores in this genus sulisequontly, but as yet I have not 

 been succt^ssful in finding many stages. 



Oeiieral couclusious. 



In the following paragraphs I shall attempt to put some 

 interpretation on the above-discussed phenomena and endeavour 

 to sketch out tlic line, along which the filamentous forms devcr 

 loped from the unicellular. Much of what follows is not new, 

 but I consider its recapitulation necessary for a füll understan- 

 ding of the facts. 



The simplest form, that has been examined, is Gloeocapsa 

 and there seems no reason to suppose that its structure differs 



