Has altered and added to HES’s list [compiled for Bibliographia zoologiæ et geologiæ, edited by Louis Agassiz and enlarged by HES, (1848–54)].

On zoological nomenclature CD cites a case in which he believes more harm than good would be done by following the rule of priority. Thinks the rule of the first describer’s name being attached in perpetuity to a species has been the greatest curse to natural history. Every genus of cirripedes has a half-dozen names and not one careful description.

Sends a paper he once wrote [missing] on the subject [of zoological nomenclature].

Responds to CD’s two objections to the principles involved in the "Rules of zoological nomenclature": (1) that strict enforcement of the rule of priority would cause much inconvenience, and (2) attaching name of the first describer in perpetuity puts a premium on careless description by "species mongers".

HES’s arguments are of great weight, but CD cannot yet bring himself to reject well-known names for obscure ones. Sends four cases that he thinks will stagger HES. Cites his problems in classifying cirripedes. CD cannot bear to give new names, yet may do wrong to attach old ones. Not one species is correctly defined. The harm done by "species mongers".

The priority rule has only diverted vanity to a rush to be first. Has no objection to CD’s suggestion that good books be quoted in preference to first descriptions if there is a chance by this means of developing this silly vanity into ambition to advance knowledge. Still, this must not affect the rule of priority. Responds to CD’s four cases.

HES’s letter will fructify to some extent: CD will try to be more faithful to rigid virtue and priority. Would not adopt his own notion in cirripede book without prior approval by others. Will not append "Darwin" to any of his species. Feels sure many others share his aversion.

Asks HES’s opinion on retention of generic name Conchoderma.

Clarifies the notion and use of type-species and applies it to CD’s problem with Conchoderma.

Thanks HES for solving his problem. Has some difficulty with HES’s type-species. In arranging genera in a natural order it is often impossible to say which species should be considered the type.