136 
B. Millard Griffiths. 
a few minutes and during this time the distortions of the cell- 
membrane make the construction of the chloroplast very obvious. 
On the other hand, if strong formalin is used, no such effects 
are produced. A solution of 20% formaldehyde (made by adding 
an equal volume of 40% solution to the water in which the organisms 
are), causes no distortion beyond a very slight shrinkage of the cell. 
The cilia do not exhibit swelling at the extremities, but merely lose 
their stiff appearance and become irregularly flexuose. (Fig. 14 D, 
shows a specimen fixed in this way). Subsequent dilution of the 
solution to 2 or 1% does not cause osmotic blistering. 1 
Slight shrinkage of the cell is also produced by strong iodine 
solution. Most of the specimens in Figs. 13 and 14 are fixed in the 
latter 
Remarks on the Cilia. On referring to Fig. 15, C, F and H, it 
will be noted that the cilia show a peculiar swelling at the extremities. 
It is not a case of curling up, because under such circumstances 
the unaltered part of the cilium would run to the side of the swollen 
part, and not to the middle. The cilium does not become very 
much shorter, as it apparently does in true cases of curling up 
(compare the two cilia in Fig. 15, H). Several examples of the latter 
were noted, but these differed totally from the swollen cilia. 
In the living state the cilia are thick and firm, but at death 
they lose their firmness (Fig. 13, D), except when the cell has become 
over-turgid through osmotic action induced by re-agents. The 
rigidity of the cilia under the latter conditions is quite remarkable 
(Fig. 15, B). The absence of blisterings on the sides of the cilium, 
and the symmetry of the swelling at the extremity, seems to suggest 
that in this organism, the cilium is not a homogeneous rod but rather 
a structure in which the peripheral part is of a denser character 
than the more central portion. 
Diagnosis : —Pyramimonas delicatulus, sp. n. Cellulee pame, 
cordatae vel compressae, leviter quadri-lobulatae ; lobi chloroplasti 
cum incisione parva in extremo, cum excavatione pyriforme parva 
in parte posteriore. Stigmate caret. Long. 20-26/x, lat. 11-16//,. 
1 Dr. West suggests that the peculiar effect may be due to the 
presence of formic acid in ordinary commercial formalin. 
Possibly in the dilute solution the irritating action of the acid 
is greater than the fixing power of the formaldehyde. In the 
strong solution, however, the formaldehyde fixes the organism 
instantly. The acid has no irritant effect on the dead proto¬ 
plasm and consequently no distortion takes place. 
