ARCHER—ON A CYST-LIKE STRUCTURE, ENCLOSING STAURASTRA. 193 
present a somewhat startling appearance, nor, unfortunately, can as yet 
any light be thrown on the mystery as to how this phenomenon occurs. 
It is worthy of note that the gathering abounded with multitudes of 
this species of Staurastrum, with many instances of conjugation, show- 
ing the characteristic zygospore of this, in itself, not uncommon spe- 
cies, though not seemingly frequently to be found conjugated. 
It is, however, not very uncommon to find certain Desmidies (espe- 
cially of the genus Euastrum—for instance, 4. oblongum or E. didelta), 
completely enclosed in an elliptic or indefinitely shaped coat, which is 
smooth, without angles or tuberculations, and with colourless granular 
contents, the included desmid seemingly always effete and dead. Occa- 
sionally one sees more than one (even three or four) enclosed in such a 
‘‘ cyst,’”’ or even sometimes two distinct species soincluded. It is also 
to be seen in other genera, such as Cosmarium and Staurastrum. Yet, 
though this phenomenon does not seem to be very uncommon, it is not 
apparently noticed in any published work. 
But to say that the more definite and striking form now aren atten- 
tion to seems to be possibly the same kind of thing, is by no means an 
explanation. The present, indeed, differs in having a definite and marked 
figure, the wall thickened at the angles, and the contents decidedly of a 
green colour. In fact, a priors they might (at first glance, and before 
one catches sight of the always present Staurastrum) be taken for a 
distinct and rather large form of unicellular alga appertaining to Nageli’s 
genus Polyedrium. 
The only seemingly possible assumption in perhaps both these cases 
appears to be that these problematic organisms are of a parasitic nature, 
not living simply upon the surface or inhabiting the interior of the 
plant attacked, but surrounding and completely investing it. In one 
instance one of these triangular productions contained, besides the Stau- 
rastrum, two half-joints of Hyalotheca dissihens, thus pointing to a kind 
of swallowing up, so to say, of the included alge (Desmidiew) during 
the formation or growth of this singular organism. A question might 
arise—Could they possibly be beings of rhizopodous nature, whose food 
consisted of the Staurastra, and themselves passing through an encysted 
condition ?—that is, could they really be organisms at all comparable, 
for instance, to Cienkowski’s Vampyrella?* Itis very unfortunate that 
‘Ican communicate nothing of the development of the production now 
drawn attention to; but opposed to the foregoing view in the forms just 
now brought forward would seem to be the definite figure, mostly trian- 
gular and prismatic, the ribbed margins and swollen angles, and the 
greenish contents, 
It may not be here superfluous to observe that this production is by 
no means the same thing as that to which I have previously elsewhere 
adverted.| They are indeed perfectly distinct things, though with some 
* “ Avchiv fur mikroskopische Anatomie,” p. 223. 
ft “* Quarterly Journal of Micros. Science,” vol. xv., p. 176. 
