Classification:

• Phylum-Coelenterata
• Class-Hydrozoa
• Order-Siphonophora
• Genus-Velella

Comments:

1. 1.Velella is a marine,colonial Siphonophora.
2. 2.It has a rhomboidal or oval flat disc which is bright blue in colour.
3. 3.The float or pneumatophore is a chambered disc containing air in the chambers and bears a vertical sail or crest like ridge on the top.
4. 4.On the lower side of the disc in the center hangs a single large gastrozooid which bears its mouth.
5. 5.Gonozooids are numerous and bear medusae ,surround the gastrozooid from all sides.
6. 6.The margin of the disc of the beset with tentacle-like dactylozooids bearing nematocysts.
7. 7.Free medusae arise from gonozooids.
8. 8.It exhibits the phenomenon of polymorphism.
9. 9.Velella is a polymorphic,marine and colonial form.
10. 10.Velella is found commonly in warm seas.

Source:

1. Practical Zoology Invertebrates by S.S.Lal. 2. A Manual of Practical Zoology Chordates by Dr. P.S. Verma.