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



compressed cylinder; it becomes a little broader towards the pedal disk, but very 

 markedly so in the upper half, so that the margin of the oral disk is turned outwards 

 even when the animal is fully contracted. 



The pedal disk and oral disk are thin-walled, but the wall itself is of considerable 

 thickness ; its upper surface is smooth, for though there are oblique and longitudinal 

 wrinkles and furrows they are plainly owing to contraction. There is no circular muscle, 

 as may be gathered from the form of the anterior end of the body. A single row of ten- 

 tacles stands on the margin between the oral disk and wall ; they look like long, wide, thin, 

 membraned sacs, and do not become smaller at the ends. A firm clasp, quite 1 cm. loner, 

 runs on the outer wall of the tentacles, as a prolongation of the body-wall ; it is broadest 

 and thickest at the base, and gradually becomes narrower and thinner towards the end. 

 As the tentacles, in consequence of contraction, are turned over towards the oral disk, the 

 tentacle clasps are also bent inwards like a scimitar, many of them so much so that they 

 lie obliquely above the oral disk. I was unable to determine the exact number of the 

 tentacles, as they were bent confusedly over one another, and the friable nature of their 

 clasps prevented me from trying to separate them. They amounted, however, to more 

 than forty. 



Besides the longitudinal ridges, I found two oesophageal grooves on the oesophagus, 

 one of them much more strongly developed than the other. After I had removed the 

 pedal disk by a horizontal section, I was able to count the septa, of which there were 

 thirty-eight, separated from one another by interspaces of equal size. They appeared to 

 me all to bear reproductive organs, but only to extend partially to the oesophagus. They 

 also projected more or less towards the centre of the pedal disk. 



In this appendix I have still three forms of Actiniae to consider besides the Porponice. 

 The first was taken at Tristan da Cunha, at a depth of 1000 fathoms, and appears to be a 

 Phellia. The body, 1*3 cm. long and 1"0 cm. broad, is covered with a finely granulated, 

 brownish, leather-like cuticle, which is wanting on the short inverted part of the wall. 

 A strong circular muscle, which contracts the wall to such an extent that the entrance to 

 the oral disk is completely closed, lies in the inverted portion of the wall. I can say 

 nothing as to the number of the very small tentacles, and I was also unable to examine 

 the number and nature of the septa more minutely. 



The two other forms of Actinias were taken along with the four specimens of Cereus 

 spinosus and the single specimen of Poiponia robusta, at a depth of 1875 fathoms, on 

 June 17, 1875, at station 237 (lat. 34° 37' N. ; long. 140° 32' E.) ; like the Actinia 

 just mentioned, they had been placed in chromic acid, and were therefore but little 

 adapted for examination. 



In the one instance I had to do with an Actinia, which so strongly resembled the 

 Dysactis crassicornis described on page 44, that I was long inclined to consider it as 

 the same species. As in Dysactis crassicornis, the muscles on the oral disk and 



