STAR-FISHES, SEA-URCHINS, ETC. 79 
farthest limit. But it differs in many details of 
structure. The mouth in the Synapta is surrounded 
by a wreath of branched tentacles, into whose in- 
terior the sea-water is admitted through a system 
of vessels connecting with a madreporic tubercle. 
The latter structure, as in all other sea-cucumbers, 
is placed near the mouth.. 
Closely examined, the transparent wall of the 
body will be found to be speckled with minute 
wart-like processes, giving the animal a rough feel 
when taken in the hand. These processes under a 
microscope reveal most extraordinary forms, which 
are most nearly likened in outline to an anchor: 
hence we speak of the anchor-like spicules em- 
bedded in the body-substance, which of themselves 
' frequently offer good characters in the determina- 
tion of species. In some forms, as in the remark- 
able pangolin-like Psolus of the New England 
coast, these processes, or rather their representa- 
tives, are developed into an armor of stout over- 
lapping scales or plates. 
Placed in a dish of sea-water, the habits of this 
interesting creature can be studied at leisure, the 
regular rhythmic or wave-like motion of the body 
proving a never-failing source of surprise to those 
to whom the animal is a novelty. At some-mo- 
ments it has contracted into a nearly perfect ball, 
at other times it has straightened itself to double 
its usual length. Frequently it throws off parts of 
the posterior end of its body, accomplishing this 
curious freak either by close constriction, or by the 
forcible expulsion of its intestines. In feeding, the 
