THOUGH loth to prolong this discussion, I wish, in fairness to Dr. Mortensen and myself, to say that I did not accuse Dr. Mortensen of regarding the echinoderm metamorphosis as a case of metagenesis.

Life began on earth more than 3.5 billion years ago, but the history of humans and other vertebrates accounts for only a fraction of this timescale. Chordates (a group that includes vertebrates) and ...

CC0 Usage Conditions ApplyClick for more information. A gallery of sea urchin and starfish larvae collected from Bocas del Toro. Most marine invertebrates, including sea urchins and starfish, have a ...

WOODS HOLE, Mass. -- Scientists have a handful of standard research organisms, including fruit flies and mice, that they use to study the evolutionary development (evo-devo) of animal lineages over ...

Rudimentary details of the life cycle of the stalkless crinoids (feather stars) — derived from stalked forms and readily collectible from the water column — have been worked out. By contrast the ...

THE object of my reply to Prof. MacBride (NATURE, December 16, 1922, p. 806) was not to discuss the classification of Asteroids, but to protest against the character of his unprovoked attack on me. An ...