COMMON TIIYONE. 235 



arc withdrawn it usually appears more bulging on one 

 side than on the other. The skin is rather tough, and 

 covered all over with non-retractile suckers, which give it 

 a papillose appearance. The tentacula are ten in number, 

 large, and not always equal ; sometimes two of them are 

 much smaller than the rest, and when such is the case it 

 is in the habit of moving these two alternately towards 

 the mouth, while the others are at rest. Many Holothu- 

 riadee exhibit this custom. The tentacula are large, 

 generally whitish, and broadly pinnate. In Dr. John- 

 ston's specimens they were brown, with darker dots. The 

 hinder part of the body tapers, and the vent is stellate. 



On opening a number of specimens, 

 many of them were empty, the animal 

 having ejected its intestines. A perfect 

 one presented a well-developed intestine, 

 moderately branched respiratory trees, one 

 oesophageal sac, and numerous generative 

 tubes full of eggs, being then yellow and 

 much dilated, the eggs of a yellow colour, and not 

 arranged in any peculiar manner. This specimen was 

 taken in January ; but as several others taken at the same 

 time presented no appearance of eggs, no inference can be 

 drawn as to the animars breeding season. The teeth were 

 singular and very peculiar, being much elongated and 

 filiform, and separated from each other by rows of pen- 

 tagonal plates. There was but one oesophageal sac. Dr. 

 Johnston's had five. One specimen dissected had ejected 

 all its internal organs, saving the generative tubes ; and in 

 another there were no traces even of them. 



Dr. Johnston gives the following interesting account of 

 its habits in confinement in the paper alluded to : — " The 

 surfaces of the body," he says, " were at first partially 



