THE HOMOLOGIES OF PEDICELLARLE. 
BY ALEXANDER AGASSIZ. 
O. F. Müller, in his “ Zoologia Danica” was the first to point 
out the existence of certain organs in sea-urchins which have long 
remained a puzzle to naturalists. To these organs he gave the 
generic name Pedicellaria, and considered them as parasites of the 
sea-urchins. Of his genus Pedicellaria he describes three species 
which are now known to be either different stages of development, 
or different kinds of pedicellarice, situated in various parts of the 
shell of the sea-urchin. Our knowledge of the pedicellariz is now 
materially changed, first by the views of Delle Chiaje, who, in 
1825, figured and described the pedicellariæ of several sea-ur- 
chins and starfishes. He however no longer considers them simple 
parasites but says distinctly that they form a part of the test of 
the Echinoderms and help them in seizing their prey and taking 
hold of adjoining bodies. Much of this view has been corrobo- 
rated, and like many of the shrewd observations of Delle Chiaje 
is gaining only now the recognition it should have received 
long ago. Valentin in 1841 gives in his “Anatomy of Echinus” 
excellent figures and descriptions of pedicellariae which he con- 
siders as organs of prehension. Agassiz at that time suggested 
the possibility of their being young stages of Echinoderms, in con- 
sequence of the discoveries then made by Sars of the remarkable 
development of a species of starfish. This, it is needless to say, 
is a view he has long ago abandoned though he is most persistently 
credited with it even at the present time. Subsequently, Erdl, 
vernoy, Müller and Troschel, Sars, Stimpson, Norman and Stew- 
art have figured a number of pedicellarize of Echini and starfishes, 
and have made a more or less successful attempt to use their char- 
acters as aids in distinguishing closely allied species. An article 
on pedicellariz in the ‘‘Annales des Sciences Naturelles” for 1869, 
by Perrier, gives a large number of excellent figures of the pedi- 
cellarize of starfishes and sea-urchins ; unfortunately, except as 4 
mere accumulation of facts, it is useless, the writer ignoring what 
had been done for the last twenty years, on the very appendages 
he was describing, so that he leaves the question of their nature 
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