438 THE VOYAGE OF H.M.S. CHALLENGER. 



for which see Note under that date, and compare the account of Oniscus spinosus, Fabr., 

 1775. Some mistakes made in this paper -were corrected in an appendix. See the 

 following Note. The specimen was included in a haul made by the Challenger on January 

 28, 1873, when " the trawl was sent do-svn, in lat. 35° 47', long. 8° 23', to a depth of 1090 

 fathoms." Among other points of interest Dr. Willemoes Suhm here mentions that the 

 muscles of the thoracic legs are only very weakly developed, from which he infers " that 

 the movements of the animal are not very rapid when it is obliged to walk over the sea- 

 bottom." " The transparency of the body makes it possible likewise [to distinguish clearly 

 the cephalic ganglion and the ventral chain, consisting of five thoracic and three abdominal 

 ganglia (Plate XLIX. fig. 1). The cephalic ganglion is situated in the anterior part of the 

 head, more on the dorsal than on the ventral side ; it is 3-50 millims. in width, and is horse- 

 shoe-shaped with pointed ends. From the middle of its anterior margin two large nerves 

 run straight to the end of the antenna;, whUe from the opposite side two commissural cords 

 run backwards, traversing the head and, after having encircled the mouth, uniting with the 

 first thoracic ganglion. The nerves passing from the sides of the cephalic ganglion are all 

 employed as ocular nerves to supply the huge compound eyes. Those of the anterior end 

 are better seen, as they go to the anterior part of the eyes, while those of the posterior end 

 seem to go to the posterior parts. 



" The first thoracic ganglion is seated just underneath the ovary in the second segment, and sends 

 out the nerves for the mouth and the genital organs. The two cords then separate till they 

 are united again in the third segment in the second ganglion ; thence they run backwards 

 in a single chain and form a ganglion in each of the subsequent segments, sending nerves 

 to the legs. Altogether we find five thoracic gangHa for six segments, and in the abdomen 

 three ganglia for five segments. The last ganglion of the abdomen is more slender than 

 the preceding ones, and seems to send out nerves in different directions, especially to the 

 anus and caudal appendages. In Phronima there are ten pairs of ganglia, five of which, as 

 in the present case, are thoracic and five abdominal." Claus, 1879, it will be found, assigns 

 only four ganglia to the abdomen in the Phi'onimidfe. 



The cjecal appendage of the stomach, described by Claus for Phronima, "has, in the present 

 species, assumed so large dimensions as to have replaced the stomach, which does not exist 

 morphologically, but is physiologically represented by the ctecum." 



" The heart is an elongated tube extending from the second to the fifth segment (Plate XLIX. 

 fig. 3, (■). Probably there are three openings in it as in Phronima, one in each segment; but 

 of these nothing could be made out. 



" The respiratory organs consist of three pairs of small transparent sacdO^e giUs at the bases of 

 the second, third, and fourth pairs of feet (Plate XLIX. fig. 1, hr). They are in form and 

 number nearly the same as in Phronima." 



" Genital Organs. — The single specimen taken is a female. There is a large ovary, distinguished 

 by its rose-colour, occupying the middle portion of the first body-segment (Plate XLIX. 

 fig. 3, ov). I suspect that it consists of two ovaries lying close together, and having two 

 excretory ducts leading to the genital papilla." "The genital papilla is an elevation in the 

 centre of the ventral surface of the first thoracic segment between the two limbs [the first 

 pair of ambulatory legs], which, as I have already mentioned, are destined to bear the eggs 

 at their base, as in the females of Nymphon. The colour of the papilla is rose, with scattered 

 scarlet points produced by smaD spines on the surface of the carapace. In the centre of the 

 genital papilla there is a large spine (Plate L. fig. 6, il) with a groove leading into a 

 depression (c), in which I believe are seated the apertures of the ovarian ducts. This pit 

 is protected by two soft appendages (Plate L. fig. 6, I), answering to the valves which 

 are to be found in most female Amphipods, and in which they keep their eggs. In 

 the present species, however, they are only rudimentary, and they do not seem to be 



