of England and India. 23 
above stated, which formed a slimy layer over the surface of a drain 
adjoining a heath-bog. Out of upwards of 200 specimens, the 
largest average size was that above given. There is considerable 
variety of shape, even to that of a circular figure (4) ; but all have 
the characteristic compressed form (c)from which I havedesignated 
the species; all present a light brown colour, and most of the 
tests have that peculiar collar-like mark (ff) round the neck 
above mentioned. Neither the nucleus nor the vesicule could 
be seen in situ, on account of the opacity of the tests; and until 
one is found sufficiently transparent to admit of this, these points 
must remain undetermined. I did not meet with a single spe- 
cimen of D. pyriformis among those of D. compressa where the 
latter so abounded, although they are both very plentiful at 
their respective localities in the same neighbourhood, and both 
in ditches draining the same heath-bog ; but while D. pyriformis 
prevailed among dead leaves only, D. compressa was chiefly found 
im company only with the conjugating Alge mentioned. Still 
I found specimens of D. compressa with D. pyriformis, and am 
now inclined to believe that those which I have considered to be 
D. proteiformis, Ehr.,in my “Observations” on D. pyriformis (l.e. 
p- 250), were specimens of D. compressa, the compressed form 
of which would easily be mistaken for globularity; for, when 
passive, this species always rests on its broad surface, and its 
compressed form is not seen until it be turned over, or until the 
animal becomes active and assumes the erect position. Further, 
I am inclined to think that they must have been specimens of 
D. compressa because this species is so generally distributed 
throughout the same neighbourhood, and, lastly, because they 
did not present the “deep olive or greenish colour” which I 
now find (ap. Pritchard) is one of the characteristic features of 
D. proteiformis. It is true that the size of D. protezformis is set 
down (/. c.) as much less than that of D. pyriformis and that of 
D. acuminata, Ehr.; but this matters little, and the characteristic 
form also of D. proteiformis, viz. “ ovate subglobose,” is so near 
that of D. pyriformis, that there remains no specific difference 
that I can now see, to disunite these so-called species. Thus, 
after all, D. pyriformis, Perty, may be but a larger and more 
elongated form of D. proteiformis, Khr., in which case the original 
name should be retained for the typical form, whichever that 
may be. 
On submitting D. compressa to pressure, and crushing the 
test in water under a glass cover, as stated in my paper on D. 
pyriformis, the animal part was found to consist of protoplasm 
charged with colourless molecule, small brown cells, yellow oil- 
globules, starch-granules, the nucleus, certain large cells which 
I shall provisionally term “ reproductive,” and portions of food 
