10 
I could not find a real speeifie difference between the specimens 
of the Barents Expedition. It is remarkable that every time I 
thought I had found a difference, it appeared afterwards that it was 
too insignificant, while there never existed a correlation of characters. 
For instance the specimen in fig. 1 has otherwise formed roots than 
that of fig. 7, and the surface of the latter is more hispid, but 
the spieules are quite the same. On the contrary specimens as in 
figg. 1—4 have roots and surfaces that resemble one another totally , 
but the larger stellate spieules of 1 and 2 were not found in 4. Be- 
tween 5 and 2 there is much resemblance, but the former has not so 
many kinds of spieules as the latter, ete. The conclusion to which I 
have come is that either one must accept as many species as indi- 
viduals or, and this is apparently the best way, one must consi- 
der all these specimens as varieties of one single species. 
As „speeifie” spieules („Spieula indicantia”’) I consider the follo- 
wing ones: ac? | M.ta.d.bif. | M.ta. | st. | st”. |. And now the 
Tethea mwuricata of Bowerbank possesses these too. I don’t hesi- 
date to identify the above described Sponges with Bowerbank’s 
Tethea muricata. 
In examining exactly the elements of the skeleton we find: 
1°. ac? [„acerate”’] long, slender often nearly filiform, straight or 
flexuous. The straight ones are nearly always thicker. ' 
The smallest diameter measured only one seventh of the 
largest one, in spieules of the same length. In order to give 
an idea of the relative length and thickness of the long spieules 
I say that, a hundred times magnified, they have a length of 
11 M. and the diameter of a pencil. The ordinary short acerates 
of the Renieridae are sometimes present too. 
2°. tr. ac. [„acuate”]. The end never being swollen (as in the „spinu- 
lated’’ spieules). I think they are only modifications of the acerate 
ones. They don’t appear often. When present they have about 
the same size as the acerates; I have found specimens measuring 
11.25 m. m. AslIsaid the acerates can reach a length of 13.33 m. m. 
3° M. ta. d. bif. [„ternate, bifurcating”]. I have figured this 
form of spieules on Plate II. figg. 1, 2, 3 and 4, and there 
