100 Thk Queensland Naturalist. Vol. I. 
and length, and the character of its membrane, whether 
smooth or otherwise. 
From these data a formal description may be written 
out and compared with those in the works of reference, 
when in all probability the beginner will find no diagnosis 
corresponding with his own in nine cases out of ten. 
There may be three or four species whose diagnosis nearly 
approximate his own, but diu'ering, one in one Avay and 
another in another, nor does an examination of the figures 
in the plates always prove of great assistance, for amongst 
his specimens he has probably seen individuals looking 
exactly like the figures of three or four distinct species, 
though these individuals were unquestionably all of one 
species. These difficulties can only be surmounted by 
perseverance. In the case supposed above, for instance, 
the student’s written description of the species under 
examination should be compared, not alone with the des- 
criptions of species nearly approaching it of any one author, 
but with those of all the authors available. He then 
quickly finds the one authority differs from another, and 
that “ in the multitude of councillors there is wisdom.” 
For that Avhich seemed an obstacle sufficient to prevent 
the assignment of his specimens to some particular species 
in the diagnosis of one authority, often vanishes upon 
consulting another, especially in the matter of dimensions, 
until at last a species is found with which, upon a com- 
bined diagnosis, the specimen fully agrees, unless, indeed, 
it be a new species, and that can only be decided upon after 
a comparison with ‘every species hitherto described. 
Failure and peseverance give a splendid training, and in 
time give a quickness and sagacity in the determination 
of species which will reward the labour of acquiring these 
mental attributes. 
Having thus taken a brief review of the genus 
Spirogyra, and of the methods employed in the determina- 
tion of the species, let us noAV proceed to enumerate the 
species which have been found in Queensland. 
Spirogyra tenuissima. 
Fig. 1 represents this, the smallest known species of 
the genus. It belongs, as do also the tAVO succeeding 
species, to the section “ Cells Avith the ends replicate,” 
and exhibits both the scalariform and lateral methods of 
conjugation as shown in the figure. It appears to be met 
Avith only in isolated sx3ecimens, or a feAV threads inter- 
spersed amongst those of other species. 
The thread shoAving lateral conjugation, after Petit. 
Spirogyra Grevilleana, 
Fig. 2 is copied from a photomicrograph of the living 
plant, with the exception of the thread with two spirals, 
which is from Petit’s “ Spirogyra des Environs de Paris.” 
