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no means standing alone; they are examples of very numerous cases. 
This implies, however, that, if in certain specimens, externally cor- 
responding, in one we find spinispirae, in another not, we have not 
the slightest right to establish new species or genera on account of 
the presence or absence of spinispirae. It is beyond doubt that 
Dernpy’s sponge is not a Suberites but a Spirastrella. 
Now we find spinispirae of every description '). In many speci- 
mens of Spirastrella purpurea we find in addition to minute (but 
full grown) spinispirae of say 8—10 u length, large robust ones of 
about 12 « in diameter by a length of 75 u. In other specimens 
such giants are missed altogether. At the beginning of my investi- 
gations I believed I should be able to find specifie characters on this 
account. But I was forced to give up this view; for those large 
spinispirae sometimes measured a good deal less than stated above, 
or they possessed the Jength but not the diameter. In this respect 
again we find gradual transitions. These facts and the fact, that robust 
spinispirae are sometimes abundant, sometimes scarce or absent, 
teach us that we cannot yet establish species on account of the 
presence or absence of large spinispirae in addition to the minute 
ones. We have as little success if we try to distinguish species by 
certain microscopical details. LeNDENFRLD described a “new species” 
because of the fact that the spines of the spinispirae did not terminate 
in a sharp point, but showed a curious very minute denticulation. 
I found, however, on carefully studying the spicules with oil-immersion, 
that the “Efflorescenz-artiges Aussehen”’ appears in numerous specimens 
of the most various external appearance. 
Summa summarum: we have to face the dilemma either of con- 
sidering all the examined specimens as one species, or to establishing 
almost as many species as we examine specimens. I for my part do 
not hesitate which way to go. At present, at all events we still know 
very little about the comparative anatomy of Sponges and hardly 
anything about their comparative embryology. And vet these lowest 
Metazoa deserve to be studied carefully. Although they throw but 
little light on phylogenetic questions, and perhaps will never do so 
because they are an aberrant branch of Metazoa, in other respects | 
am convinced the Parazoa are certainly of general importance. For 
instance on account of their tissues. But the field of Spongiology is 
unexplored except by a few specialists. Not quite without reason, for 
there are many traps. 
1) Since it is impossible, for the moment, to make out whether we have to do 
with one or with more sorts of spicules, J consider them for convenience’ sake as 
one kind. 
