216 CURREY, ON FRESH-WATER ALG#. 
Nostoc minimum (? n. sp.) —Frond ellipsoidal, very minute, 
about1-120th inch, cells of the filaments somewhat square, but 
constricted in the middle on two sides, giving the filaments 
a crenate outline; vesicular cells globular and colourless. Had. 
In a pool (which dries up in hot weather) on Paul’s Cray 
Common, Kent, June, 1856. 
Fig. 27 represents this species, which, as far as I know, is 
undescribed. I have named it for convenience of reference, 
although new species of Nostoc should be admitted with 
caution, the genus even being of doubtful validity.* 
In conclusion, I have only to notice shortly the plants 
drawn in figs. 28 and 29. Fig. 28 I take to be a state of 
Chlamydococcus. The outer membrane was colourless, and 
the two internal globular cells of a clear bright ruby crimson. 
The pecularity of the plant consisted in the fact of the 
cell being filled with mimute staff-like subcylindrical bodies 
in active motion, precisely similar to the Spermatozoa of 
Vaucheria.t I watched these bodies at intervals for about 
twenty-four hours, and the motion was incessant. At the 
end of that time the cell slipped amongst some other Algze 
on the same side and was lost. Whether these little active 
organisms were really Spermatozoa, or whether they belonged 
to the mysterious bodies which, in some way or another, are 
supposed to find their way from without into the cells of 
Algz, it is impossible to say. 
The other figure (fig. 29) represents, no doubt, the 
final stage of some Volvocine$ in which the gonidia have 
become encysted. 
I notice it because the encysted cells were of a pale yellowish- 
brown colour, and covered with minute pits or depressions, 
and were altogether different from those of any other Alga 
with which I am acquainted. In Pandorina and Stephano- 
spheera, the resting spores are red, in Volvox bright orange, 
and in neither case are there any such markings as those in 
the membranes of the cells shown in fig. 29. 
* See Bayrhoffer, Entwickelung, &c.; von Thrombium Nostoe, Bo- 
tanische Zeitung, 1857, p. 137; and Itzigsohn, ‘ Phykologische Studien,’ 
Nova Acta, vol. xxiv, pp. 1839—156. 
+ See ‘ Micros. Journ.,’ Vol. 1V, Pl. III. 
t As to these bodies, see ‘ Bot. Ziet.,’ 1857, No. 14, and Pringsheim’s 
‘ Jahrbiicher,’ Part i, p. 371. 
§ I have coined this substantive to avoid the periphrasis of “one of the 
Volvocinex,” or “a Volvocineous Alga.” 
BLACKHEATH Park, 8.E., 
June 1, 1858. 
