Which of the following does NOT pertain to didermic organisms?

Didermic organisms, characterized by their body structure, have two distinct germ layers: the outer ectoderm and the inner endoderm. This is in contrast to organisms with three germ layers (triploblastic organisms), which also include a mesoderm layer. Therefore, stating that didermic organisms have three germ layers is incorrect and does not pertain to their definition.

The complexity of their structure, the presence of endoderm and ectoderm layers, and their potential for bilateral symmetry are all aspects that align with the characteristics of didermic organisms, making them applicable in this context. This distinction between the number of germ layers effectively highlights what does not define didermic organisms.