250 MECZNIKOW, ON ICHTHYDIUM, ETC. 
ninth segment, and on the sides of the body there is from the 
sixth to the tenth segment just such a one on each side. 
Besides the EL. Dwardinii upon which the foregoing re- 
marks touch, I have also examined EH. monocercus as described 
by Claperéde. I have also a few remarks to make on this 
form. 
This second kind is about 0:2 mm. long, and is easily 
distinguished through the pale colour of the skeleton, but one 
finds still further differences if one examines it closely. 
Claperéde speaks as follows about it :—“ Instead of the long 
terminal bristles of H. Dujardinii, we find in E. mono- 
cercus an unequal tail-tuft of bristles which really belongs 
to the back, so that the anus comes to lie underneath it; as 
to the rest, the exo-skeleton of HE. monocercus agrees with 
that of H. Dujardinii.”” But in spite of this plain statement 
the skeleton of both these kinds is strikingly different; not 
only in EZ. monocercus is the division of the exo- skeleton into 
four parts wanting, but it differs from the former species in 
that the unequal bristles on the posterior segments increase 
in size. The tail-bristle in L. monocercus agrees therefore in 
no way with the last bristle in LE. Dyardinii, as Claperéde 
believes. The correctness of my idea is borne out not only 
by the circumstance that this bristle lies above the anus, but 
also by a peculiarity of HL. monocercus, which Claperéde had 
overlooked, and which first induced me to oppose his ideas. 
This peculiarity is that EH. monocercus consists of eleven 
segments, and not twelve, as HE. Dwjardinii. Therefore the 
last furcal segment is wanting in E. monocercus, and the last 
segment in this species agrees with the last but one in the 
other. The difference in the bristle armature of the two 
kinds consequently reduces itself to this—namely, to the 
presence of the dorsal, that is, the side bristles on the last 
segment of EH. monocercus. 
But at the same time I think J may consider this kind to 
be only a young condition of E. Dujardinii. 
As regards the inner inaccessible organisation of our 
animal I can only add some remarks to those of Claperéde. 
I must first state that our animal possesses a layer of side 
muscles under the integument, whose single broad structure- 
less fibres stand far from one another, and run through the 
whole length of the body. I may also add, that the sexual 
organs described by Claperéde cannot be counted as male or 
any other part of the generative apparatus, because they 
consist of an ill-defined mass of cells, which lie on each side 
in the four last segments, and have no plain communication 
with a tube or efferent canal, as Claperéde supposes. 
