Potamon fluviatile crabs' unusual size, up to , and longevity (up to 15 years) are also interpreted as evidence of a long-established population, by analogy with island gigantism. On the island of Malta, "Potamon fluviatile" is rare and restricted to a few locations in the west of the island. On Gozo, there is a single population which inhabits a stretch of river only long. In the Balkan Peninsula, "Potamon fluviatile" is known to occur in Croatia, Montenegro, the Republic of Macedonia, Albania and Greece. There are four species of "Potamon" in the Balkans, and "P. fluviatile" is replaced by "Potamon ibericum" in
If This Is a Man not merely its lexical but also its inner faithfulness." Robert S. C. Gordon writes that Levi went on to develop a close relationship with Reidt. The German edition contains a special preface addressed to the German people, which Levi said he wrote out of passionate necessity to remind them what they had done. "If This Is a Man" is often published alongside Levi's second work of witness, "The Truce" (Italian title: "La Tregua"). The book is introduced by a poem. The construction "If .." invites the reader to make a judgment. It alludes to the treatment of people as "Untermenschen"