*J00 l' r i 1 s (• h , SliKÜos 011 Cyauophyceae. 



living coiulition. althoup;]! stains ni:ik(> tlicin show np iiioro 

 promiiK'Ully. In youiig stagcs tlie niucli smallei' size of tli(i cells 

 iiiakes tlie determination of details a great difficulty; nor is tlie 

 inner inve.stinent vory strongly developed at that period and 

 c'onso((iiently it is very difüciilt to disiiiigiiisli between it and a 

 possil)lo vudiniontaiy cell-slicalh. The two investments of the 

 protopla.st only become sliaiply delined in well-advanced sporo- 

 genous filainents, — a faet, wliicli is not surprising, wlien we 

 consider, tliat tlieir origin (as an excretion from the ^Drotoplast) 

 is the sanie. It is natural to expeet that the cell-sheath Avill 

 become morc defined, as the protopLnst becomos older, and will 

 reach its most marked differentiation, when the sjDore develops^ 

 i. e. when the necessity of a lirmer outer covering is fully 

 realised. 



As tlie cells of a filament pass over into the sporogenOus 

 condition the transverse limits of the cell-sheaths of adjacont 

 cells become better defined (cf. fig. 5 and 8). Gradually also 

 by the increase of the colourless intercellular septum the cells 

 move further apart , whilst the cell-sheath increases in extent 

 and closes in round the open ends, so that the outer Investment 

 ultimately forms a complete sheath i'ound the matiu'e spore 

 (hg. 6). As the sheath closes in it envelopes a portion of the 

 intercellular septum so that the sheath or exospore of the 

 spore (fig. G, ex) surrounds a complete inner investment or 

 endospore (fig. 6, en). The romainder of the intercellular 

 septum has swollen up considerably and has become invisible; 

 it is the cause of the now more or less wide Separation of 

 the spores. The spores thus exhibit two Avell-marked mem- 

 branes, as in the cases, dcscribed by Gomont and Borzi. 

 Witli regard to the spores the former (loc. cit. p. 238) remarks: 

 ,,La spore enfin, lä oü eile existe, est bien, comme on l'admet 

 generalement, produite par l'encystement crune cellule vegetative.. 

 Elle possede un exospore oü se retrouvent les enveloppes de 

 celle-ci, et un enrlospore produit au 'moment de la maturite, et 

 identique par ses proprietes ä la membrane cellulaire vegetative.'' 

 Brand (03, p. 34) also considers that „das Endospor . . . erst 

 bei der die Keimung einleitenden Zellverjüngung entsteht, . . . 

 nur an ganz reifen Exemplaren vorhanden ist"^. Gromont and 

 Brand thus regard the endospore as producecl at the moment 

 of maturity; in Änahacna both the envelopes of the spore are 

 however present long before maturity is reached and, if either, 

 it is certainly the exospore in my opinion, which is newly 

 formed. The process is scarcely one which comes under the 

 name encystment. During the development of the spores the 

 cells increase very much in size and the fully-developed spore 

 is 2- — 3 times larger than the ordinary vegetative cell; there is 

 however very little change in colour^j in the species. which I 



1) The cell-contents are sliglitly yellowisli-gi'een, biit coiild scarcely he 

 caUed colonred (cf. Braud 03, p. 38). 



