REPOKT ON THE PYCNOGONIDA. 113 



Nijmphon in a much more rudimeutaiy state. Nobody would conclude, however, from 

 their presence that the first ganglion was originally composed of four gangha ; Ijut the 

 supposition of its being formed of three nuclei loses at the same time much of its value, 

 and the ventral part of the proljoscis must be considered as l)eing innervated Ijy the same 

 original ganghon 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 Nymjihoii and Phoxichilidium, 

 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 caU the paired proboscideal nerves. They end, like the 

 azygous proboscideal nerve, by entering a ganglion, placed at a1)0Ut the same distance 

 from the end of the proboscis as the ganglion of the azygous proboscideal nerve. These 

 tluree gangUa are united by a ring, which runs between the outer wall of the proboscis 

 and the c4iitinous wall of the oesophagus, among the numerous muscles which ran from 

 the one wall to the other. 



So far my description quite agrees with that of Dohrn, as given above. Ho\\'ever, a 

 considerable difference arises from the fact that the ganglia which were seen by Dohrn 

 are not to be considered as ganglia of the azygous or paii'ed proboscideal nerves, but 

 as being really the terminal ganglia of three strong nerve buncUes, 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 oesophagus. The 

 discovery of these three ganglionic nerve buncUes has been very fortunate. It is curious 

 that they have hitherto been always overlooked, and especially that Dolu-n did not 

 observe them. But then it must he considered that these nerve l^undles are placed 

 among numerous muscles running over and beneath them, and making a preparation 

 totally impossible. A successful longitudinal section, made exactly above or IdcIow a 

 buncUe, 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 s}Tiipathetic system 

 of higher animals, yet their structure shows in general the same relative distrilxitiou 

 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 l^undle of nerve fibres, which, posteriorly at irregular, anteriorly at more 

 recrular distances, are surrounded l)y groups of ganglion cells. Thus each of the 



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(ZOOL. CUALL. EXr. — PART X. — 1881) -''^ 



