REPORT ON THE PYCNOGONIDA. 113 
Nymphon in a much more rudimentary state. Nobody would conclude, however, from 
their presence that the first ganglion was originally composed of four ganglia; but the 
supposition of its being formed of three nuclei loses at the same time much of its value, 
and the ventral part of the proboscis must be considered as being innervated by the same 
original ganglion as that which gives off the nerves for the palpi. 
I believe there can be no doubt that we have here the original condition of the 
nervous system ; at the same time this fact may be considered as suggesting the opinion 
that the palpi originally belonged to a pair of appendages which coalesced to form the 
two undermost of the three parts of which the proboscis is composed. 
The two front nerves of the first thoracic ganglion in Nymphon and Phoaichilidium, 
and the strongest of the two front nerves of the same ganglion in Colossendeis, 
enter the proboscis and run forwards exactly in the middle of the two ventral parts 
of the proboscis, which I compared (note on p. 14) with the carpels of a monocoty- 
ledonous fruit. These nerves I call the paired proboscideal nerves. They end, like the 
azygous proboscideal nerve, by entering a ganglion, placed at about the same distance 
from the end of the proboscis as the ganglion of the azygous proboscideal nerve. These 
three ganglia are united by a ring, which runs between the outer wall of the proboscis 
and the chitinous wall of the cesophagus, among the numerous muscles which run from 
the one wall to the other. 
So far my description quite agrees with that of Dohrn, as given above. However, a 
considerable difference arises from the fact that the ganglia which weré seen by Dohrn 
are not to be considered as ganglia of the azygous or paired proboscideal nerves, but 
as being really the terminal ganglia of three strong nerve bundles, composed of nerve 
fibres and ganglia, which run longitudinally below or above the three stout proboscideal 
nerves, so that they lie between these nerves and the wall of the cesophagus. The 
discovery of these three ganglionic nerve bundles has been very fortunate. It is curious 
that they have hitherto been always overlooked, and especially that Dohrn did not 
observe them. But then it must be considered that these nerve bundles are placed 
among numerous muscles running over and beneath them, and making a preparation 
totally impossible. A successful longitudinal section, made exactly above or below a 
bundle, is the only way to detect it. I call these bundles ganglionic, for although 
I do not believe that their function is analogous with that of the sympathetic system 
of higher animals, yet their structure shows in general the same relative distribution 
of ganglion cells and nerve fibres as in the case of the ganglionic system of higher 
animals. 
Fig. 6 on Plate XVIII. shows the position of these nerves in the proboscis; while 
fig. 8 shows a part of one of them more strongly magnified. Each of them (g) consists 
of a strong bundle of nerve fibres, which, posteriorly at irregular, anteriorly at more 
regular distances, are surrounded by groups of ganglion cells. Thus each of the 
(ZOOL, CHALL. EXP.—PART x.—1881.) K 15 
