3. SCHIZOPODA.--This order of animals for the most part delicately beautiful, has for the moment five families--Lophogastridae, Eucopiidae, Euphausiidae, Mysidae and Anaspididae. In the Euphausiidae the digitiform-arborescent branchiae, as if conscious of their own extreme elegance, remain wholly uncovered. In the two preceding families they are partially covered. In the Mysidae the branchiae are wanting, and some would form this family into a separate order, Mysidacea. In _Anaspides_, a peculiar fresh-water genus discovered in 1892 by G. M. Thomson on Mount Wellington, in Tasmania, the gills are not arborescent, and there are seven segments of the trunk free of the carapace (fig. 2). A membranaceous carapace separates the Eucopiidae from the more solidly invested Lophogastridae. Among many papers that the student will find it necessary to consult may be mentioned the "_Challenger_" _Report_ on Schizopoda, by Sars, 1885, dealing with the order at large; "British Schizopoda," by Norman _Ann. Nat. Hist._ (1892); "Decapoden und Schizopoden," _Plankton-Expedition_ (Ortmann, 1893); "Euphausiidae," by Stebbing, _Proc. Zool. Soc._ (London, 1900); _Mysidae of the Russian Empire_, by Czerniavski (1882-1883); and _Mysidae of the Caspian_, by Sars (1893-1895-1897). 4. STOMATOPODA.--This order, at one time a medley of heterogeneous forms, is now confined to the singularly compact group of the Squillidae. Here the articulation of the ocular segment is unusually distinct, and here two characters quite foreign to all the preceding groups come into view. The second maxillipeds are developed into powerful prehensile organs, and the branchiae, instead of being connected with the appendages of head and trunk, are developed on the pleopods, appendages of the abdomen. At least three segments of the trunk are left uncovered by the carapace. The developing eggs are not carried about by the mother, but deposited in her subaqueous burrow, "where they are aerated by the currents of water produced by the abdominal feet of the parent." An excellent synopsis of the genera and species is provided by R. P. Bigelow (_Proc. U.S. Mus._ vol. xvii., 1894). For the habits and peculiarities of these and many other Crustaceans, A. E. Verrill and S. I. Smith on the _Invertebrates of Vineyard Sound_ should be consulted (1874). The general subject has been illuminated by the labours of Claus, Miers, Brooks (_"Challenger" Report_, 1886), and the latest word on the relationship between the various larvae and their respective genera has been spoken by H. J. Hansen (_Plankton-Expedition Report_, 1895). The striking forms of _Alima_ and _Erichthus_, at one time regarded as distinct genera, are now with more or less certainty affiliated to their several squillid parents. [Illustration: FIG. 3.--_Pseudocuma pectinatum_, Sowinsky.]