[From the American Journal op Science. Vol. XIX, March. H

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Das System, der Medusen (.Erste H&lfte des ersten Theils:System der Craspedoten) ; von Dr. Ernst Hajckel. i-x and360 pp., -with 20 plates. Jena, 1879.—Since the publication ofEschscholtz’s System der Akalephen, an immense number of addi-tions to our knowledge of some of the smaller groups of Medusaehave been made. The principal attempts to revise the classifica-tion of the group as a whole we owe to Gegenbaur (1856) andAgassiz (1862). Their own observations were based either uponEuropean or American species, and they could do but little toward