No7.. 1921.] CYTOLOGICAL STUDIES ON PORPHYRA TENERA. 213 



peculiar, the mode of the reduction division of the zygote-nucleus is 

 also different from that of the highly organised one. 



Phylogenetic Observation. 



It has been shown by recent investigations that there are grada- 

 tions betvsreen the diffuse t\^pe and primitive mitosis type, as defined 

 by Gardner (3) in the incipient nuclei (12) of Cyanophyceae and 

 also, several intermediate types are present between the amitotic and 

 primitive mitotic divisions (3) in the nuclear division of those plants. 

 The nucleus of Porphyra may be regarded as a kind of incipient 

 mucleus, though it differs in some respects from the highly organized 

 type in the nucleus of Cyanophyceae. As stated in the foregoing 

 paragraphs, the method of the nuclear division of Porphyra has a 

 close resemblance with that of Cynechocystis aquatilis, a kind of 

 Cyanophyceae, in the presence of three chromatic filaments and 

 primitive mitosis. From this, it seems most probable that Porphyra 

 has a close affinity with Cyanophyceae so far as nuclear phenomena 

 are concerned. Moreover, according to Nakano and Higashi (7) 

 Porphyra tenera possesses both phycocyanin and phycoerythrin, and 

 the same is reported in some species of Cyanophycese : Phylloderma 

 sacrum (by Nakano and Higashi), Oscillaria sancta (by Gaidukov), 

 O. caldariolum (by Kylin), Phormidium Retzii var. nigro-violacea 

 (by Boresch). The coexistence of the two sorts of colouring matters 

 also tells an intimate relation existing between Porphyra and Cyano- 

 phycea;. But the presence of stellate chromatophore and the sexual 

 act in the reproduction distinguish Porphyra from Cyanophyceae. 

 However, this gap between them will be bridged to some extent by 

 Porphyridium cruentum, whose systematic position had been wandering 

 between Bangiales and Cyanophyeae until it was finally settled as 

 one of the lower members of Bangiales (6, lie). It has a stellate 

 chromatophore with a pyrenoid in its centre, and excentrically placed 

 incipient nucleus. The nucleus probably shows the primitive mitosis 

 in its division, though the investigation on this point has not been 

 fully carried out (6). The resemblance of so many characters just 

 mentioned to those of Porphyra, but the complete absence of sexual- 

 ity in this unicellular organism, shows a close connection of Porphy- 

 ridium with Cyanophyceae. According to Molisch,* the phycoery- 

 thrin is present in Porphyridium, but the phcocyanin has not been 

 detected. 



* Molisch: Mikrochemie der Pflanzen. 



