... ingroups. Within each group the parts differonly in degree, in largeness or smallness,softness and hardness, smoothness orroughness, and the like (LOC. CIT., i., 4,644b). These passages show ... essentialresemblance underlying the differences ofcertain parts. He classes together nails and claws, the spines of the hedgehog, and hair, as being homologous structures. Hesays that teeth are allied to bones,Sanguinea ... the same, differing only in excessor defect, he says, "But some animalsagree with each other in their parts neitherin form nor in excess and defect, but haveonly an analogous likeness,...