LINNEAN SOCIETY OF LONDON. Ixxi 



p. 340), but that species are (p. 353) genealogical individualities, 

 subordinate to tliat of a pbjlon, wbicb it is practicaUj necessary 

 and possible to distinguish and to name. Then follows his defi- 

 nition of a species, which I subjoin in a note, as to me it appears as 

 difficult to translate as to apply practically when translated *. 



Prof. C. Claus, of Marburg, has published a handbook to the 

 ordinary classification of animals, under the title of ' Grundziige der 

 Zoologie,' in two vols. 8vo ; and in a meftioir on the Copepod Crus- 

 tacea of Nice has shown a strong tendency to the adoption of 

 Darwinian theories. The continuation by Dr. Gerstacker of the 

 Arthropod section of Bronn's 'Klassen und Ordnungen des Tliier- 

 reichs,' mentioned in my address of 1866, advances but very slowly. 

 Prof. Gegenbaur's latest work on Comparative Anatomy, ' Unter- 

 suclmngen zur vergleichenden Anatomic der Wirbelthiere,' com- 

 prises two jiarts, the first relating to the carpus and tarsus, the 

 second to the shouldergirdlc of Vertcbrata and the pectoral fins of 

 fishes. Dr. Peters of Berlin, whose active services in the cause of 

 zoology you have acknowledged by electing him to fill the last va- 

 cancy in the list of your foreign members, has recently published 

 memoirs on the Aye- Aye, on Bats, and on Eared Scales. A post- 

 humous memoir by the late H. Eathke, on the development and 

 structure of the Crocodile, the last great work of its distinguished 

 author, has been brought out, under the care of Dr. v. Wittich, in 

 the Nova Acta Naturae Curiosorum. 



Kner and Steindachncr have, in the Transactions of the Academy 

 of Munich, described the new genera and species of fish from Cen- 

 tral America collected by Moritz AVagner, who has himself added 

 an Essay on the hydrographical conditions and on the geographical 

 distribution of freshwater fishes in the states of Panama and 

 Ecuador, containing several statements of considerable interest — 

 amongst others, that there are some (although, he admits, very few) 

 species quite identical in the marine estuaries of the opposite sides 

 of the isthmus, contrary, he says, to the dictum of Darwin in the 

 * Origin of Species,' the merits of which work he otherwise fully 



* " Die Species oder organisclie Art ist die Gesammtbeit aller Zeugnngskreise 

 welche unter gleichen Existenzbedingungen gleiehe Formen besitzen." If -we 

 render this as " the species is tlie sum of all the generation-cycles which, 

 under similar conditions of existence, possess similar forms," the question sug- 

 gests itself, What is a generation-cycle ? In reading his long chapter on the 

 subject, in the hopes of obtaining a clear explanation, I only felt more be- 

 wildered ; nor can I find any clue to an important point in the definition — 

 what degree of variation similarity admits of. 



