1903.] The Cell Structure of the Cyanophycecc. 405 



If the cells of any of the larger species of Cyanophycea>, with some- 

 what elongate cells, be stained with hsematoxylin, according to the 

 method of Heidenhain, or with a solution of fuchsin, the substance of 

 the central body becomes clearly defined from the peripheral cytoplasm. 

 It does not possess a definite membrane, but in certain cells, generally 

 near the ends of the filaments, it is found inside a vacuolar space 

 in the centre of the cell, so that it is clearly separated from the 

 cytoplasm by the delicate vacuolar layer or membrane (fig. 1). In the 

 older cells this vacuolar space seems to disappear, but in Tolypothrix, 

 even in the oldest cells of the filament, it can still be recognised (fig. 2). 

 The central body is usually, in young cells, surrounded on all sides by 

 the peripheral coloured layer, but in some forms, and especially in 

 older cells, it extends from one end of the cell to the other, 

 and is in close contact with the transverse walls (fig. 2), whilst the 

 peripheral coloured cytoplasm forms a cylinder around it. The central 

 body appears in such cases to be intimately concerned in the formation 

 of the cell wall, and is in close connection with the cyanophycin 

 granules which are often found in contact with it in certain species, and 

 which are usually regarded as of the nature of reserve food substances. 

 It seems not unlikely that the central body is concerned in the 

 formation of these granules. In one case which I examined, the 

 central body was almost entirely free from chromatin, whilst the 

 cyanophycin granules, with which it was in close contact, were, 

 contrary to their usual character, stained deeply in haematoxylin, the 

 central body being only very slightly stained. I have also obtained 

 a distinct reaction for phosphorus in granules, which by their position 

 and general appearance were cyanophycin granules, whilst the central 

 body gave only a very slight indication of it. 



The substance of the central body consists of a more or less regular 

 granular network (figs. 1, 2, 3). The granules are small, and usually 

 uniform in size, but here and there may sometimes occur a granule 

 or granules larger than the rest. The ground substance of the net 

 work upon which the granules are placed stains only slightly in 

 nuclear stains, and appears to correspond to the linin or plastin network 

 of the nuclei of higher forms. The granules themselves stain deeply in 

 nearly all the nuclear stains ; they resist the action of artificial 

 digestive fluid, and give a distinct, and in some forms a strong reaction 

 for phosphorus when treated according to the method devised by 

 Macallum. They probably, therefore, correspond to the "central 

 substance" of Zacharias, and to those portions of the central body 

 which are found by Macallum to contain masked iron and phosphorus. 

 From a consideration of these facts it is difficult to escape the con- 

 clusion arrived at by Macallum that "there can be ... very little 

 doubt that a chromatin-like substance is present in the central body.' 7 

 And when we further consider the structure of this central body, its. 



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