The embryology of insects is entirely a study of the last century.
Kowalevsky or a bug is invaginated into the yolk at the head end, the portion of (1871 and 1887) on the embryology of the water-beetle Hydrophilus the blastoderm necessarily pushed in with it forming the amnion.
Xx., 1880; Kingsley, " The Embryology of Limulus," Journ.
If the Phylactolaemata were evolved from the type of structure represented by Phoronis or the Pterobranchia, the Gymnolaen ata should be a further modification of this type, and the comparative study of the embryology of the.two orders would appear to be meaningless.
In embryology the method finds its expression in the limitation of comparisons to the corresponding stages of low and high forms and the exclusion of the comparisons between the adult stages of low forms and the embryonic stages of higher forms.