The Protochordata or Prochorda are simpler forms of the chordate animals in which the notochord is wholly or partially formed and the vertebral column and skull are lacking (hence Acrania). This division includes a heterogeneous (polyphyletic) group of animals of the phylum Chordata, most of which are fairly related to the vertebrates but none possesses [...]
The Tunicata (or Urochordata) are hermaphrodite marine chordate animals, contained in secreted tunic in adult stage, which are usually sessile and degenerate, and may be solitary or colonial, fixed or free; the chordate characters in these are well represented in their larval stage in which the notochord is restricted to the posterior part of the [...]
Asexual reproduction It is of rare occurrence. It is reported by Gilchrist (1923) in Balanoglossus capensis. During summer the juvenile phase reproduces by cutting off small pieces from the tail end. The separated part later on develops completely into an adult sexual type in next winter. Sexual reproduction The sexes are separate but there is [...]
J.F. Eschscholtz who discovered Balanoglossus in 1825 in Mashail Island described it as a worm-like holothurian. The discovery of gill-slits in this animal by Kowalewsky (1865) led to creation of a special class Enteropneusta by Gegenbaur (1870). Bateson (1885) included them in Phylum Chordata. Hyman (1959), however, placed them near Echinodermata and gave Hemichordata a [...]
COELOM Early developmental stages of Balanoglossus possess a spacious coelom lined with peritoneum. It is enterocoelous in origin. As the adult condition is attained, the coelomic epithelium gives rise to the connective tissue and muscle fibres. Hence the coelomic cavity is obliterated. The coelom as a whole is divided into three parts. These include one [...]
