Let me share with you a difference between protostomes and deuterostomes.
| Aspect | Protostomes | Deuterostomes |
| Cleavage Pattern | Spiral cleavage (unequal and diagonal divisions) | Radial cleavage (symmetrical divisions) |
| Fate of Blastopore | Forms the mouth in most cases | Forms the anus in most cases |
| Coelom Formation | Schizocoelous | Enterocoelous |
| Mesoderm Development | Typically from two bands of cells (determinate) | Typically from pouches of the archenteron (indeterminate) |
| Regulative Development | Limited ability for regulation during development | High ability for regulation during development |
| Segmentation | Typically, if present, is not well-pronounced and not repeated | Well-pronounced and often repeated segmentation |
| Fate of Blastula Cells | Fate of cells often determined early in development | Cells retain greater flexibility in their fate |
| Embryonic Development | Rapid and determinate development | Slower and more regulative development |
| Embryonic Induction | Inductive interactions often limited | Extensive inductive interactions during development |
| Examples | · Annelids · Mollusks · Arthropods | · Echinoderms · Chordates (including vertebrates) |