what is balanoglossus??

A Balanoglossus is an ocean dwelling acorn worm belonging to Phylum Protochordata. It is of great zoological interest, because being a Hemichordate ( having at least half notochord) it acts as an evolutionary link between invertebrates and vertebrates. Balanoglossus resembles sea squirts in the way that it possesses branchial openings or "gill slits". Their heads may be as small as 2.5 mm (1/10 in) or as large as 5 mm (1/5 in). It has a stomochord too( i.e. the gut chord within the collar) 

Protochordates like Balanoglossus, Amphioxus, Herdmania, etc. have a notochord, which is either absent or does not run the entire length of the animal’s body.

Some other features of Balanoglossus are:  1. It has a single chambered heart.  2. This marine animal is triploblastic and coelomic.    3. It is bilaterally symmetrical( i.e.the left and right halves of the body have the same design).