The author scrutinizes fossil fishes, centring on a large placoid specimen from Stromness, and employs careful anatomical description and original woodcut illustrations to challenge contemporary development theories. He surveys fossil assemblages across Palaeozoic, Secondary, and Tertiary strata, assesses cerebral and embryonic features, compares placoid attributes with other vertebrates, and considers molluscan and plant remains to reconstruct ancient environments. Drawing on these observations, he contends that the rock record requires cautious interpretation and that popular notions of progressive, unguided development rest on incomplete or misread evidence, while urging restraint against materialist inferences unsupported by paleontological fact.