Nov., 1921.] CYTOLOQICAL STUDIES ON PORPHYRA TENERA. 207 



Method. 



Materials were collected at several culture grounds in Tokyo 

 Bay during the winters of 1920 and 1921, from November to March, 

 which are seasons of this alga. As the fixing reagent, a mixture of 

 equal parts of two percent solution of osmic acid and two percent 

 aqueous solution of acetic acid was in the most cases used ; the 

 material was left in this solution for a half to one hour and after an 

 hour's washing in water, transferred to V4, percent alcohol, then to V2 

 percent and so forth and finally to parafiin. This method always gave 

 the best result. Besides, Flemming's weaker solution with an addition 

 of eqnal volume of acetic acid, or concentrated aqueous solution of 

 picric acid was often tried. Much difficulty was experienced in 

 obtaining a good preparation of the material, since the cejl contents 

 became contracted after the material was transferred to alcohol, 

 though it was satisfactorily well fixed. This was always the case 

 when picric acid or modified Flemming's fluid was used. To prevent 

 this contraction, the fixed material was transferred to Carnoy's fluid 

 before it was brought to alcohol. Carnoy's fluid caused the swell- 

 ing of cell contents, and thus counteracted the effect of alcohol. 

 But in the material thus treated the chromatophore became thickened 

 and the nucleus was often scarcely differentiated. Sections were cut 

 2-3// thick. Some material was mounted in toto. A varietj of stains 

 have been used ; of these, Heidenhain's iron alum haematoxylin prov- 

 ed the most useful ; light green, acid fuchsin and ruthenium red 

 have occasionally been employed as the counter staining, of which 

 ruthenium red was the best for differentiating the fine structure of 

 the chromatophore. 



Yegetative Cell and its Division. 



Vegetative cells of the thallus except in the basal part are 

 cuboid, covered with thin walls and are embedded within a common 

 hyaline mass, which is agar-like in nature. The cell membrane shows 

 no cellulose reaction with Congo-red and chlorzinc iodine, but is 

 stained in brilliant pink red colour with ruthenium red. Hence the 

 presence of pectic substance in the membrane leaves no room for 

 doubt. As to the chemical nature of the hyaline mass which is 

 stained with light green, I can say nothing. But it is worth men- 

 tioning that the external surface gives no cuticular reaction when it 

 is treated with Sudan III. This hyaline intercellular substance is 



