Of the fourteen original specimens found by Mr Busk, several have been lost. The one that he himself gave me I handed over to Prof. Leuckart, and it is figured in his work (‘Die mensch. Par.,’ s. 586). A second is preserved in the museum attached to the Middlesex Hospital, and a third is contained in the Museum of the Royal College of Surgeons. This last-named specimen is the best of the original set. It supplied me with the few details of structure figured in outline in my ‘Introductory Treatise’ (fig. 42, p. 123), published in 1864; and it also in part formed the basis of the description of the species communicated to the Linnean Society in June, 1859 (“Synopsis of the Distomidæ,” p. 5, ‘Proceedings,’ vol. v). The late Dr Lankester, it is true, was the first to give a distinctive title to this entozoon (_Distoma Buskii_); but as the discoverer objected to this nomenclature, and as Dr Lankester’s proposed terms were unaccompanied by any original description, I requested Mr Busk to suggest a new name for the worm, which he accordingly did. As I subsequently pointed out, Von Siebold had already employed the compound title _Distoma crassum_ to designate a small fluke infesting the house-martin (_Hirundo urbica_); but for reasons similar to those which contributed to set aside Dr Lankester’s nomenclature, the title adopted in my synopsis at length came to be recognised by Leuckart and by other well-known helminthologists. Before this recognition took place, Dr Weinland, of Frankfort, had so far accepted Lankester’s nomenclature as to call the species _Dicrocœlium Buskii_. In my judgment there are no sufficient grounds for retaining Dujardin’s genus. Further, I may observe that, in addition to the above-mentioned specimens, two others are preserved in the Museum at King’s College. Thus, only five out of the fourteen specimens are still in existence.