REPORT ON THE PYCNOGONIDA. iba 
rounded spot distinguishable by its transparency. The optic nerves are represented by 
two strong bundles of nerves, arising as in Colossendeis megalonyx (Pl. XVIII. fig. 4, 0) 
laterally from the dorsal anterior surface of the ganglion. These nerves divide into 
stronger and feebler branches, and the latter have small ganglia between them. Such 
small ganglia are present also on the interior surface of the small transparent spot 
representing the rudimentary eye. They are in relation partly with the nerve fibres 
of the so-called optic nerve, partly with the complicated system of nerves and ganglia, 
which covers in this species as in the other species of the same genus, the internal 
surface of the integument. In this species of the genus Colossendeis, and from what I 
have seen of the matter, the same is the case in Colossendeis leptorhynchus and C. 
megalonyx, the optic nerve-bundles are really integumentary nerves, giving off the 
nerve-branches, which, as will be shown hereafter, extend all over the inner surface of 
the integument, having everywhere ganglia between them, and, as a rule, at small dis- 
tances from one another. 
I feel inclined to consider the condition of the eye, and of its innervation as described 
for Colossendeis proboscidea, as the original condition in the Pyenogonida. As an 
example of the most highly developed condition, I wish to describe that of Nymphon 
brachyrhynchus. Dorsally the supra-cesophageal ganglion gives off two nerves, which 
are at their origin quite covered over by ganglion cells (Pl. XVIII. fig. 11 C. 0’). 
Where they arise from the ganglion, the distance between the two nerve-bundles is not 
very considerable; they diverge slightly till they reach the base of the oculiferous 
tubercle. Here each of these nerve-bundles divides into two branches which run 
horizontally, the one towards that part of the integument which is before, the other 
towards that behind the oculiferous tubercle. On reaching the integument each of these 
two branches divides into numerous smaller nerves and nerve-fibres ; moreover, they 
send upwards numerous nerve-fibres, which penetrate the oculiferous tubercle and extend 
till they reach the outer wall of the eye. There can be no doubt, therefore, that the eye 
is innervated by nerve-fibres not united together so as to form a distinct optic nerve. 
The same mode of innervating the eye I observed in Nymphon strémii.. For the 
study of the innervation of the rudimentary eye of Nymphon robustum 1 got good pre- 
parations also. A part of one of these is figured in Plate XVIII. fig. 5. We have the 
same nerve-bundles covered by ganglionic cells ; they do not, however, divide immediately 
into the stronger integumentary and smaller optic nerves, but before doing so they enter 
a comparatively large ganglion (fig. 5, g) from which these nerves are seen arising. 
This same ganglion gives off also the nerves for the sete, which in this species are 
present in considerable number at the tip of the oculiferous tubercle. 
1 This quite corresponds with Dohrn’s observations, that the optic nerves give off also branches to the curious 
organs observed by him between the eyes. I believe these organs are rudimentary in Nymphon, in Colossendeis proboscidea 
they are totally wanting. 
