Affinities and Systematic Position of Balanoglossus With non-chordate

Affinities with non-chordates :-

(B) With Pogonophora :-

(a) Similarities :-

(i) Coelom → Enterocoelic

(ii) Nervous system → Intraepidermal

(iii) Gonads → In trunk region

(iv) Pericardial sac → Present

(b) Dissimilarities :-

Features	Balanoglossus	Pogonophora
Main nervous system  concentrated at	Mesosoma	Protosoma
Coelomoducts	Absent	Present
Alimentary canal	Present	Absent

Remark :-

Young (1983) opposed the resemblances between the two groups (as stated by Barington,1965; Parker and Haswell, 1972; and Mc Ferland et al, 1985), claiming the similarities are superficial.

Affinities with non-chordates :-

(B) With Echinodermata :-

(a) Similarities :-

(i) In Adult Form :-

(i) Coelom → Divisible in 3 successive parts anterior-posteriorly.

(ii) Nervous Plexux → Subepithelial

(ii) In Larval Form :- 

Tornaria resembles Bipinaria in.

(i) Pre-oral ciliated bands → Present

(ii) Cleavage → Holoblastic & equal

(iii) Apical Plate → With a turf of cilia.

(iv) Blastopore → Become Anus in adult.

(v) Enterocoelic coelom → Present.

(b) Dissimilarities :-

(i) In Adult Form :-

Features	Balanoglossus	Echinodermata
Water vascular system	Absent	Present
Pharyngeal gill slits	Present	Absent
Stomochord	Present	Absent

(ii) In Larval Form :- 

Features	Balanoglossus	Echinoderms
Eye-spot in apical plate	Present	Absent
Telotroch	Present	Absent

Remark :-

Based on resemblances; Hemichordates & Echinoderms are thought to be originated from some common remote ancestor (Hymen,1959) and Barrington,1965). H.B fell (1963) denied it on the ground that similarities were due to larval convergence in similar mode of living.