PORPHYRIDIUM CRUENTUM NAEGELI 
335 
and often hard to see, and in ''house cultures" it even disappears in most 
cells. In regard to the nucleus he said: "Although now the existence of a 
nucleus is a priori very probable, I could, after completely dissolving the 
sheath, never with certainty show one. The nucleus-like structures which 
one sees in living as well as in fixed stained material, are not only in regard 
to size, form, and position very variable, but appear sometimes single 
and sometimes many. All usual methods of staining have given me, through 
repeated investigations, very uncertain results." 
Kufferath, utilizing the technic of bacteriology, was able to get a pure 
culture of Porphyridium to grow in various gelatinous media. The alga 
growing thus showed a great increase in size, at times reaching a diameter 
of 24 /X, and showed somewhat of a variation in its method of division. 
Two daughter cells sometimes developed within the body of the mother 
cell, and even tetrads occurred. Kufferath denied the existence of a pyrenoid 
in Porphyridium and stated that what has been taken for a pyrenoid is an 
optical effect due to a convergence of the light rays by the plastid. In 
regard to the nucleus also his findings are quite different from Brand's. 
He writes: ''The nucleus, which has been seen only by Schmitz, is colored 
by the usual stains; it is oval, somewhat refractive and applied against 
the cell wall ; it is small and we have not been able to distinguish its intimate 
structure." 
A most obvious explanation for this divergence in the results of the 
various investigators would be furnished if the case of Porphyridium were 
analogous to that of Protosiphon and Botrydium. Different species of 
plants, no matter how much alike externally, would hardly give identical 
results on an intimate investigation, especially if their ancestry were diverse 
and they had evolved along parallel lines. While it is possible that more 
than one genus has been investigated under the name of Porphyridium, and 
this possibility should not be overlooked in future investigation of this 
much studied but little known alga, the facts at present do not substantiate 
this hypothesis. The present investigation has often shown in the same 
plant two characters, each of which has been described and had its existence 
denied by some of the aforementioned authors, whose views were just the 
opposite in regard to its accompanying character. 
The diameter of Porphyridium in the material studied varies from 5 
to 9 jjL, the smaller cells almost uniformly being in the resting condition. 
The jelly secreted by each cell forms an individual sheath about that cell 
and, when division takes place, the two daughter cells are in the same 
sheath, which follows the constriction of the cells quite intimately, and 
lengthens as the cells draw apart. The portion of the sheath between the 
two cells becomes drawn out into a strand or stalk (figs. 10, 11, 39). As 
these cells were originally within the sheath of the mother cell, which itself 
was on a stalk, we frequently find the mother stalk branching into two 
