F r i t s <• h . Stiidies on Cyanojjli yceae. 203 



At tlie same time yoiing stages of GJoeocapsa are always 

 to be fonncl in wliich tlie cell-slieath. is nnrecognisable and in 

 these tlie clemonstration of tlie inner investment is a very difti- 

 cult matter; even witli the lielp of elironiic acid I was not 

 able to render it visible in a satisfactory maniier, owing appa- 

 rently to the very considerable contraction in this case. Brand 

 lias already (00, ]). -i) commented on tliis diflicnlty. bnt mentions 

 a case, in wliieli .,ganz frisclie Teilungsprodukte einer Zelle . . 



abnormer AVeise durch eine farblose sclilaucliälinliclie 



Brücke zusammenliingen", whicli is probably due to special 

 development of the inner investment in the case in question; 

 I have met witli similar phenomena (i. e. cases, in which two 

 adjacent cells were connected by the much drawn out transverse 

 septum) in Anabaeiia^ and in my opinion tliey tend to eoiiürm 

 the gelatinous natui'e of the investment. 



The portion of the investment, that I have called the cell- 

 sheath in Oloeocapsa., was also recognised by Nägeli (49, p. 47, 

 48), for he says: „Die Zellwandung (i. e. the eiitire investment) 

 ist sehr dick und in der Regel das Zelllumen mehrmals über- 

 treffend, selten demselben bloß gleichkommend 



An der AVandung kann meistens die schmale Zellmembran und 

 die breite Hüllmembran unterschieden werden''. Nägeli 's ,,Zell- 

 membran" corresponds to the cell-sheath and the „meistens" 

 indicates, that he already observed. its occasional absence; the 

 „Hüllmembran" refers to the external mucilage. Brand (00, 

 p. 7) also came to the conclusion, thatNägeli's „Zellmembran^'' 

 was not the actual cell-membrane , for he says: „jene öfters 

 bemerklichen Zonen, welche Nägeli im Auge zu haben scheint, 

 gehören aber der Gallerte an, und die eigentliche Zellhaut von 

 Gloeocapsa (alpina) ist, wie bereits angedeutet, mit den gewöhn- 

 lichen Hilfsmitteln überhaupt nicht zur Anschauung zu bringen". 

 In the case of C/iroococru.s lielveticus Klebs CSQ . p. 391) states 

 that: „Jede intensiv blaugrüne feinkörnige Zelle besitzt eine 

 äußerst zarte, dünne Zellwand" and here also I have no doubt 

 that the cell-sheath is meant. 



AVhen the colonies of a Gloeocapaa or GJoeotliece are sub- 

 jected to a 33 ^'o Solution of chromic acid the external stratihed 

 sheath is tirst attacked and gradually dissolved away; it takes 

 some little time before the acid reaches the cell, but tlien, as in 

 Änahaoia, the cell-sheath slowly disappears, unless the cells have 

 reached the mature size. The inner investment, as already men- 

 tioned, is vei'y difhcult to discern afterwards. 



A few words may be added on the genus Merlsmopodia, 

 in which a largo number of cells are bound together by tliin 

 transparent mucilage to form Hat plates; owing to the sniall 

 size of the colls specimens, staiuod witli Yosuvin, were examined. 

 The cell-sheath in these is well marked in contrast to the inner 

 investment; it is eitlier coniined to pairs of cells or surrounds 

 larger groups of them, when rapid division is taking place. The 

 former state of affairs is bv fax the commonest and it is noti- 



