hagfish

lack vertebrae

jawless toothlike keratin structures

cartilage 

lamprey

jaws

larva: suspension feeders

adults: attach to fish

cartilage 

cartilage  (lost bone)

spiral valve

cloaca

can use jaws and pharyngeal muscles to breathe

bony fish

mucus membranes

swim bladder

flexible fins 

excretory systems

(planaria)

(annelids)

(insects) 

planara: protonephridia through bulbs to nephridiopore

annelids: metanephridium: nephrostome through bladder to nephridiopore

insects: malpighian tubules to gut to rectum