12 MyxophycesB 



granules as separate chromatophores, and stated that each granule may contain chloro- 

 phyll, carotin, and phycocyanin in variable proportions. Both Olive and Gardner 

 concluded that there was no definitely organized chromatophore. Hieronymus ('92) 

 described the cell as possessing a chromatophore consisting of small granules of chlorophyll 

 strung like beads on a network of threads which extended through the peripheral part of 

 the protoplast in which the phycocyanin was dissolved. 



Nadson ('95) describes the peripheral cytoplasm as vesiculated, and states that the 

 chlorophyll and phycocyanin are contained in the walls of the alveoli. The pigmented 

 portion he regarded as functioning both as cytoplasm and chromatophore. Massart ('02) 

 considered that the pigmented layer, although morphologically not a true plastid, yet 

 functioned as such. Phillips ('04) also regarded the outer pigmented zone as one in which 

 the functions of the chromatophore were not yet divorced from the functions of the 

 cytoplasm. 



The location of the pigment in the cells of the Myxophycese does 

 not appear to be entirely uniform throughout the group. The pigmented 

 zone is more indefinite in some cases than in others, and instances have been 

 recorded in which the pigment has extended into the incipient nucleus. 

 It is scarcely possible, in view of the evidence, to accept Hegler's and Kohl's 

 ideas that the numerous minute coloured granules are each of them 

 chromatophores. There is convincing evidence that the Myxophycean 

 protoplast is of a primitive character, and most of the modern investigations 

 show that nothing of the nature of a true chromatophore has yet been 

 evolved, except in the puzzling genus Glaucocystis. The pigmented zone 

 undoubtedly functions as a chromoplast and at the same time carries on the 

 normal functions of cytoplasm, no complete differentiation having as yet 

 taken place between the plastid and the cytoplasm. 



Cell-sap vacuoles do not normally occur in the protoplasts of all Blue- 

 green Alga?, and when present it is highly probable that they are often 

 due to pathological conditions. In Oscillatoria decolorata, which has de- 

 generated into a saprophyte and lost all trace of colour, the protoplast is very 

 much vacuolated. In the cytoplasm of normal cells of Chroococcus macro- 

 coccus, Miss Acton has found that small vacuoles are not at all uncommon, 

 and that vacuolation begins in this species near the periphery of the 

 protoplast and proceeds towards the nuclear region. 



INCLUSIONS IN THE PROTOPLAST. Within the protoplast of the Blue- 

 green Algae are several kinds of granules, which have been described by 

 various authors under different names. Many conflicting statements have 

 been made concerning the staining of these granules, although much of 

 the discrepancy may have been due to differences in fixation, and to the 

 use sometimes of alkaline and sometimes of acid reagents. There are six 

 inclusions deserving of special mention. 



(1) Central granules. These are found scattered among the meshwork 

 of the incipient nucleus (the so-called ' central body '), and they stain well 



