Believes in the "perfect indefiniteness & frequently the vast length of the interval" between consecutive geological formations. Thus has little respect for arguments against CD based on the absence of transitional forms in the geological record. States that species found through series of beds do vary: some Silurian species have many synonyms which are really varieties of greatly differing ages. CD’s theory accounts for the progressive inprovement, multiplication and increase in complexity that can be seen, but which may often be only relative.