1898-99. | ON THE CYTOLOGY OF NON-NUCLEATED ORGANISMS. 453 
than one central body. The material which he used must have been in 
a pathological condition, for it is only when Cylindrospermum mazus is 
ill-nourished that any one of its cells possesses similar vacuoles and a 
plurality of central bodies. 
It is obvious, therefore, that a study of the cells of the Cyanophycee 
involves the employment of a large number of methods of manipulation, 
and a regard for material in all conditions of nutrition. The latter 
requisite also entails a careful attention to the various conditions in 
which the organisms are usually found, and an acquaintance with the 
modifications that a varied environment brings about. These conditions 
and these modifications are, at present, not fully known, but what we do 
know helps in determining what is the typical structure of the cell in 
this class. 
I have, therefore, in all cases used material from each species which 
was found to be in an active state of growth. This is a safeguard of 
great value. The material which one may collect from any locality 
may be in the resting stage, a stage in which also, perhaps, changes 
analogous to those of involution in Bacteria may manifest themselves. 
The only material which one can confidently regard as normal is that 
which grows in the laboratory, and which .can be examined from hour 
to hour, the change in the volume of the material being an indication of 
its active growth, 
The species’ used in these studies were JMzcrocoleus terrestris 
Desmazieres (M7. vagznatus Gomont), Oscellaria Froehlichiz Kiitzing 
(O. limosa Agardh), Oscillaria natans Kiitzing (O. tenuis Agardh), 
Oscillarta tenerrima Kiitzing (O. amphibia Agardh), Oscillaria princeps 
Vaucher (O. maxima Kiitzing), Cylindrospermum majus Kiitzing, Toly- 
pothrix tenurs Kiitzing, Tolypothrix rupestris Kiitzing, Nostoc commune, 
Rivularia sp., Gleocapsa polydermatica, Lyngbia sp., Scytonema sp. 
The hardening reagents employed were: corrosive sublimate in 
saturated aqueous solution, in saturated alcoholic solution, and in con- 
junction with picric acid, picric acid in saturated solution, Flemming’s 
chrom-osmio-acetic mixture in strong and weak solution, osmic acid in 
one per cent. solution, alcohol absolute and of ninety-five per cent. 
strength. I have used also aqueous and alcoholic solutions of iodine. 
The best preparations were made with the picric acid and corrosive 
1 Gomont, ‘*‘ Monographie des Oscillariées, (Nostocacées homocystées),” Annales des Sciences Nat,. 
zieme Série, Botanique, Tome XV, p. 263, Tome XVI, p. ar. 
Also, Bornet and Flahaut, ‘* Revision des Nostocacées heterocystées contenus dans les principaux 
herbiers de France,” Annales des Science Nat., Botanique, 7ieme serie, Vols. III, 1V, V and VII. 
