SUMMARY OF THE REPORT. 



1. Of the forty-one species of Pycnogonida dredged during the voyage of H.M.S. 

 Challenger and the cruise of the " Knight-Errant " thirty-three are new to science. 



2. Of the nine genera represented in those collections three are new. 



3. Those genera which range most widely geographically are also those w^hich range 

 most widely in depth. 



4. There are deep-sea species, but true deep-sea genera do not seem to exist. 



5. The Pycnogonida form a distinct and very natural group (class) of arthropodous 

 animals. Their common progenitor (their typical form) must be considered as a h}^o- 

 thetical Pycnogonid with three-jointed mandibles, multi-jointed palpi, and ovigerous legs 

 with numerous rows of denticulate spines on the last joints. 



6. This class of the Arthropoda may be thus characterised : — Arthropoda breathing Ijy 

 the general surface of the body, which body consists of a cephalothoracic, three thoracic 

 segments, and a rudimentary abdominal segment. The cephalic part of the cephalothoracic 

 segment bears anteriorly a proboscis, consisting of three coalesced parts, one prse-oral 

 (labrum ?), two post-oral ones (mandibles ?), and three paii* of cephalic appendages, the 

 first two of which in the adult state sometimes have become rudimentary, the third pair 

 being always present at least in one of the two sexes. The first pair of these appendages 

 represents the antennae, the two others are post-oral. The thoracic part of the cephalo- 

 thoracic segment and the three thoracic segments are each furnished with a pair of long 

 eight-jointed legs, into which the alimentary canal sends ofi" long coeca. 



7. The function of the integumentary cavities is primarily respiratory. 



8. The typical form of the nervous system shows a supraoesophageal and five 

 thoracic ganglia. The supraoesophageal ganglion gives ofi" the nerves for the mandibles 

 (antennse), the integumentary nerves, and a strong nerve for the proboscis. Besides these 

 it probably gives ofi" nerves for the intestine (sympathic nerves). The first thoracic 

 ganglion consists of two coalesced ganglia, and gives ofi" four pairs of nerves, two pairs 

 innervating the proboscis, then the pair of palpar nerves, and finally those for the ovi- 

 gerous legs. The following four ganglia give ofi" the nerves for the four pairs of legs ; the 

 last ganglion gives sometimes two sometimes one pair of nerves for the abdomen. 



9. In addition to the nerves mentioned above the proboscis is innervated by three 

 strong bundles of nerves and ganglia united by a stronger and some feebler secondary 

 oesophageal nerve rings. 



(ZOOL. CHALL. EXP. — PART X. — 1881.) K 19 



