28, has the form of a bottle-shaped mass of undifferentiated embryonal cells, covered by a thin cuticle, but without any trace of further organization.
"On the Origin and Metamorphoses of Insects"
Sir John Lubbock
Hugo de Vries distinguishes between partial and embryonal variations, or between variations and mutations, only the last-named being heritable, and therefore of importance for the origin of new species.
"Darwin and Modern Science"
A.C. Seward and Others