C. Mereschkowsky on Wagnerella borealis. 289 
in spirits. Now the individuals preserved in alcohol, even 
when afterwards placed in glycerine, become entirely opaque ; 
one can see nothing of their contents or of their internal 
organization; and consequently it is only possible to form an 
idea of the nature of the animal from the characters presented 
by their exterior. But this exterior bears witness strongly 
in favour of the animal being nothing but asmall sponge; the 
spicules of two different kinds produced by the animal itself, 
above all, suggest this opinion as to the nature of the animal. 
Since then I have had the opportunity of seeing some 
hundreds of specimens of Wagnerella borealis in the Bay of 
Naples, as also the preparations made of it by M. Paul 
Mayer, who has had the kindness to show me these as well as 
his drawings. The preparations of these animals coloured 
with tincture of cochineal have especially served to convince 
me that I was entirely deceived in assigning them a place 
among the sponges. | am now convinced that itis an organ- 
ism probably belonging to the group Heliozoa, in the class 
Protozoa; for there is no doubt that the protoplasmic mass is 
not formed of cells ; it isin all only a single cell with a single 
nucleus, which divides only for the purpose of propagation into 
two, four, and eight nuclei, as described by M. Paul Mayer*. 
It is therefore, in the first place, to correct this error that 
I write this note, and, further, to confirm the identity of the 
Wagnerella borealis of the White Sea with that which occurs 
in the Bay of Naples, and which has been recognized as a 
Protozoan by the researches of M. Paul Mayer. 
In the second place, it is to rectify another error that I 
committed in describing the animal discovered by me in the 
White Sea, and an error of a much less pardonable nature than 
the former. I described the spicules that cccurred in Wagne- 
-rella borealis as being of a caleareous nature. A more careful 
examination of the object has convinced me that in this I have 
committed a profound and gross error, the spicules being sili- 
ceous as in all the Heliozoa. It was in reading the fine work 
by M. Biitschli on the Protozoa} that I recognized the neces- 
sity of correcting this error, which I hope will be excused me, 
seeing that I committed it at the very outset of my zoological 
studies. 
As to the question whether the spicules are produced by the 
animal itself, or elements foreign to the organism and selected 
by it from among the spicules of sponges, I think that M. 
* Paul Mayer, “ Wagnerella borealis,” Zool. Anzeiger, Bd. ii. 1879, 
pp: 857, 358. 
+ Butschli, Bronn’s ‘Klassen und Ordnungen, Band i. Protozoa, 1881. 
Ann. & Mag. N. Hist. Ser. 5. Vol. viii. 20 
