REPORT ON THE PYCNOGONIDA. Ill 



rounded spot distingiuHlialjle by its transparency. The optic nerves are represented by 

 two strong bundles of nerves, arising as in Colossendeis megalonyx (PI. XVIII. fig. 4, o) 

 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, pai-tly with the complicated system of nei-ves 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 ofi" the 

 nerve-branches, which, as wUl be shown hereafter, extend all over the inner surface of 

 the integimient, 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 Pycnogonida. As an 

 example of the most highly developed condition, I wish to describe that of Nymphon 

 hrachyrhynchus. DorsaUy the supra-flesophageal ganglion gives ofi" two nerves, which 

 are at their origin quite covered over by ganglion cells (PL XVIII. fig. 11 C. o'). 

 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 Nymphori stromii. For the 

 study of the innervation of the rudimentary eye of Nymphon rohustum I 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 setse, which in this species are 

 present in considerable number at the tip of the oculiferous tubercle,^ 



^ This quite corresponds with Doliru's observations, that the optic nerves give off also branches to the curious 

 organs oljserved by him between the eyes. I believe these organs are rudimentary in Nymphon, in Colossetideis proboscidea 

 they are totally wanting. 



