Perhaps you should try some spelling variations:
philosophical sketches » philosophical sketch, philosophical sources, philosophical researches
philosophical species » philosophical aspects, philosophical queries, philosophical space
philosophical studies » philosophical study, philosophical societies, philosophical subjects

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((((philosophical species) OR (philosophical studies))) OR (philosophical sketches)) species.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((philosophical species) OR (philosophical studies))) or (philosophical sketches)) species".
• Adding a wildcard symbol may retrieve word variants: ((((philosophical species) OR (philosophical studies))) or (philosophical sketches)) species*.