Huxley on Lacinularia socialis. 
9 
of the neck of the animal, or rather upon the under surface of 
the trochal disc, just where it joins the neck, and therefore 
behind and below the mouth, there is a small hemispherical 
cavity (fig. 4 6) (about l-1400th of an inch in diameter), Avhich 
seems to have a thickened wall, and is richly ciliated within. 
Below this sac, but in contact with it by its upper edge, is a 
bilobed homogeneous mass (figs. 2 and 4 n) (about l-800th 
of an inch in diameter), resembling in appearance the ganglion 
of Brachionus, and running into two prolongations below, but 
whether these were continued into cords or not I could not 
make out. 
I believe that this is, in fact, the true nervous centre, and 
that the sac in connection with it is analogous to the ciliated 
pits on the sides of the head of the Nemertidae, to the 
" ciliated sac " of the Ascidians, which is similarly connected 
with their nervous centre, and to the ciliated sac which 
forms the olfactory organ of Amphioxus. 
Mr. Gosse has described a similar organ in Melicerta 
ringens^ and 1 have had an opportunity of verifying his obser- 
vations, with the exception of one point. According to this 
observer, the cilia are continuous from the trochal disc into the 
cup ; so far as I have observed, however — and I paid par- 
ticular attention to the point — the cilia of the cup are wholly 
distinct from those of the disc. 
The interesting observations of the same careful observer 
upon the architectural habits of Melicerta would seem to 
throw a doubt upon the propriety of ascribing to the organ in 
question any sensorial function. 
But however remarkable it may seem that an animal should 
build its house with its nose, we must remember that a 
similar combination of functions is obvious enough in the 
elephant. 
No eyespots exist in the adult Lacinularia. In the young 
there are two red spots on the upper surface of the trochal disc, 
which are stated by Professor Ehrenberg to be seated upon 
" medullary masses " (Mark-Knotchen). I could not satisfy 
myself either of the truth of this statement or tiie contrary, 
in consequence of the difficulty of distinguishing the separate 
tissues in the young animal. 
I may be permitted here to say a word upon the nature of 
the " calcar " or " respiratory tube " of Ehrenberg, which 
exists in so many Rotifera. For his first notion, that it is 
connected with the reproductive system, Professor Ehrenberg 
has substituted the idea that it is a respiratory tube, through 
which currents of water are conducted into tlie cavity of the 
body, and bathe the "trembling organs" which he calls 
