6 



Myxophycese 



well be regarded as au 'open nucleus' in contradistinction to the 'closed nucleus' of 

 higher plants. Nadson ('95) considered the central body only as an aggregation of the 

 middle alveoli of an alveolar protoplast, distinguished from the outer portion of the 

 protoplast by the fact that it is the region where the so-called chromatin granules are 

 exclusively or especially concentrated. He concluded that the central body corresponded 

 to the nucleus of other organisms, but differed in its morphological peculiarities. Wager 

 ('02) stated that the central body was vacuolated, and possessed granules which stained 

 deeply with nuclear stains, resisted the action of digestive fluids, and gave strong reactions 

 for phosphorus and masked iron. He considered that the granules had all the characters 

 of nuclein and were comparable to the chromatin of a true nucleus, 



Guillerrnond ('06) stated that the central body consists of a hyaloplasm in which 

 there is an achromatic reticulum containing granules of chromatin. He regards it as 

 a true chromatic network and compares it to the 'chroinidial apparatus' described in 



Fig. 4. Dermocarpa fucicola Saunders. Left figure, section of mature cell in vegetative 

 condition, showing a thin layer of cytoplasm surrounding a definite network of 'chromatin.' 

 Right figure, section of cell containing mature gonidia. Very highly magnified (after 

 Gardner). 



certain of the Protozoa. There is no spireme ; there are no chromosomes, nor is there 

 any division of the chromatin granules; and the division is amitotic. Swellengrebel ('10), 

 from observations on only one species of Calothrix, found an alveolar achromatic ground 

 substance in which were embedded granules and filaments of chromatin, with a more or 

 less uneven distribution. He also stated that the distinction between the groundwork of 

 the central body and the surrounding cytoplasm is somewhat slight, and sometimes the 

 chromatin granules are diffused throughout the cell. The latter condition was observed 

 by Guillermond, but only in vacuolated cells, and he therefore considered it merely as 

 a pathological condition. Brown ('11) found in a species of Lyngbya a nuclear body 

 consisting of a mesh of fine fibres embedded in a clear substance resembling nuclear sap. 

 Small granules were scattered along the fibres, the latter staining like linin and the former 

 like chromatin. 



Still more recent work carried out by Miss Acton on various members of the 

 Chroococcaceae is largely confirmatory of Nadson's view that the protoplast is alveolar 



