300 LILIAN J. GOULD. 
some kind of contents and a nucleus, but I found no appear- 
ance of internal structure other than that described above. 
I am inclined to think that he, too, sometimes confounded 
refringent bodies with vacuoles, since he describes a falling in 
of the walls of the former which occurred with some reagents, 
and I found a crenellation of this kind to be very character- 
istic of the food-vacuoles under certain conditions. The re- 
fringent bodies divide by constriction, and in fig. 6 the process 
is seen near completion. M. Pénard (‘ Archives des Sciences 
physiques et naturelles,’ tome xix, 1893) says that colouring- 
matters have little or no effect upon them, and that they are 
either structureless or coutain vacuoles. Possibly he looked 
upon the crescentic areas as vacuoles, or, as he evidently used 
different reagents, he may have failed to distinguish the 
refringent bodies from the food-vacuoles, which generally have 
contents of some sort. 
The Vacuoles. 
The vacuoles proper were of two kinds, viz. (1) large non- 
contractile vacuoles, which did not stain (figs. 2 and 8), and (2) 
food vacuoles of varying size, which were found with and 
without contents. These contents in all cases stained freely 
with carm-alum and picro-carmine, and the vacuoles were 
further distinguishable by the greater thickness, and often by 
the crenellation of their walls (fig. 8). The “ vesicles” of 
Professor Bourne, which greatly outnumber the vacuoles, and 
must be placed apart on account of their having in P. viridis 
chlorophyllogenous contents, are perhaps, as suggested by 
Professor Lankester, not to be regarded as “ vacuoles,” but 
as corresponding to the glanzkorper of P. palustris. 
The Nuclei. 
With regard to these I have nothing new to add. The 
nuclei were lodged in the nodes of the protoplasmic network, 
and presented, as described by Greeff and others, a finely 
granular structure with several nucleoli in the middle, and 
deeply-staining chromatin granules arranged peripherally in 
