The theory that ontogeny recapitulates phylogeny was originally offered by?

What type of appendages do sponges cnidarians roundworms annelids mollusks arthropods echinoderms and vertebrate have? jointed, not jointed, absent  

Ascientific idea becomes valid when it is what?

Been sitting here trying to take this test and don't know this answer! place the events of a feedback mechanism associated with body temperature in the correct order. ·nerve cells send message from skin to the brain ·body returned to normal temperature around 98.6 degrees f ·temperatures regulation center in the brain sends out signals ·body temperature exceeds 98.6 degrees f ·sweat glands throughout the body activate to cool off skin surface it is a 1 through 5 question in biology!