While they lack specific excretory, respiratory, and circulatory systems, they do have a nervous system, muscular system, and reproductice system.
(they; lack; specific excretory, respiratory, and circulatory systems) (they; do have; a nervous system, muscular system, and reproductice system)
they they
lack do have
specific excretory, respiratory, and circulatory systems
a nervous system, muscular system, and reproductice system