With respect to the steps by which these curious organs have been evolved, Mr.

Agassiz infers from his own researches and those of Mr.

Muller, that both in star-fishes and sea-urchins the pedicellariae must undoubtedly be looked at as modified spines.

This may be inferred from their manner of development in the individual, as well as from a long and perfect series of gradations in different species and genera, from simple granules to ordinary spines, to perfect tridactyle pedicellariae.