SUMMARY OF THE REPORT. 
1. Of the forty-one species of Pycnogonida dredged during the voyage of H.MLS. 
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 which range 
most widely in depth, 
4. There are deep-sea species, but true deep-sea genera do not scem to exist. 
5. The Pyenogonida form a distinct and very natural group (class) of arthropodous 
animals, Their common progenitor (their typical form) must be considered as a hypo- 
thetical Pycnogonid with three-joited 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 by 
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 pra-oral 
(labrum ?), two post-oral ones (mandibles ?), and three pair 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 antenn, 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 off long cceca. 
7. The function of the integumentary cavities is primarily respiratory. 
8. The typical form of the nervous system shows a supracesophageal and five 
thoracic ganglia. The supracesophageal ganglion gives off the nerves for the mandibles 
(antennee), the integumentary nerves, and a strong nerve for the proboscis. Besides these 
it probably gives off nerves for the intestine (sympathic nerves). The first thoracic 
ganglion consists of two coalesced ganglia, and gives off 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 off 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 
cesophageal nerve rings. 
(ZOOL. CHALL, EXP,—PART x.—1881.) ~ K 19 
