140 
DR. R. YON WILLEMOES-STTHM ON THE 
The lateral horns (Plate 13. fig. 17) are said by Claparede and Buchholz to be 
movable. In our case they certainly are provided with muscles, running up to them 
from the dorsal centre of the carapace, and fixing on a chitinous ring which looks 
like a septum in the upper portion of the horn (Plate 13); but I have never seen 
a movement in these horns, though I examined many living specimens. Their outer 
chitinous covering is inverted at the top (where it has two prolongations and many 
setse attached to it), and runs inside up to the place into which the glands pour 
their contents, and which is also the place of attachment for the muscles (fig. 17, q). 
Here two large glands and two smaller ones terminate. Whether these large glands, 
the bottoms of which are fixed to the carapace by threads of connective-tissue, are in 
communication with the general glandular system of the carapace I doubt, as I never 
saw such a communication. With all the smaller glands, however, which run up to the 
different processes (fig. 16, gl and pr, fig. 17, pr, and fig. 22, gl), this is undoubtedly the 
case; they form a large glandular network all through the carapace, just as Dohrn 
has already described in Archizo'ea gig as. 
On the lateral horns we remark a few very small spines, the only spines which have 
not a gland opening at the top. 
A question which has been left open by Dohrn is the innervation of these different 
organs, about Avhich he could say nothing, having only spirit-specimens at his disposal. 
I have examined the larvae alive under the highest power, and have arrived at the 
following result. The only exterior appendages, which are very likely sensitive, are 
small reflecting hairs (figs. 16 & 17, y ), to the base of which runs a somewhat varicose 
nerve-fibre. No sensitive appendages are to be found at the top of the lateral horns 
nor of any of the processes. The glands, however, are in connexion with nerves, and 
it is by no means difficult to find nerves sending off branches in all directions. One 
may trace these easily to the base of glands which terminate in the larger processes. 
In one case (fig. 16, c) I have also seen a ganglionic cell close to one of these processes, 
sending apparently a fibre up to it, but not being connected with the large lower nerve 
(fig. 16, n) which gave a branch to the gland. 
Neither the small nervous hairs nor the innervation of the glands is at all extra- 
ordinary, as in many of the lower animals, which are favourable objects from their 
transparency, something of the same kind has been observed. 
Dohrn, when speaking about these lateral horns, says that as Claparede and Bucn- 
iiolz have declared them to be movable, and described muscles running up to them, 
and as on the other side the evidence given for a transformation of the first appendages 
into the antennae with the sucker seems not to be sufficient, he is inclined to think 
that these organs are modifications of the lateral horns. He adds that they must 
have a very important function, because otherwise their complicated structure would 
not be intelligible. Nevertheless my observations, as I shall show below, -make me 
think that Krohn, Mecznikow, Pagenstecher, and Claus, who maintain against 
Burmeister and Darwin the first-mentioned way of metamorphosis, are perfectly 
