lively after putting them in a bucket of salt water had then for the first time come into free contact with the element in which they were soon to live; but at the same time it can hardly be doubted that the water penetrates into the marsupial sac, since these young have fully developed gills. The size of the young compared with that of the mother is very remarkable, being full one-third its length in the one, and nearly so in the other species. Indeed these young Embiotocæ, not yet hatched, are three or four times larger than the young of a Pomotis (of the same size) a full year old. In this respect these fishes differ from all the other viviparous species known to us. There is another feature about them of considerable interest, that while the two adults differ markedly in coloration, the young have the same dress, light yellowish olive with deeper and brighter transverse bands, something like the young trout and salmon in their parr dress." [Illustration: FIG. 312.—Viviparous Perch (male), _Hysterocarpus traski_ Gibbons. Battle Creek, Sacramento River. (Photograph by Cloudsley Rutter.) ] CHAPTER XXII CHROMIDES AND PHARYNGOGNATHI =SUBORDER Chromides.=—The suborder _Chromides_ contains spiny-rayed fishes similar to the perch-like forms in most regards, but strikingly distinguished by the complete union of the lower pharyngeal bones, as in the _Holconoti_ and _Pharyngognathi_, and still more remarkably by the presence of but one nasal opening on each side. In all the perch-like fishes and in nearly all others there are two nasal openings or nostrils on each side, these two entering into the same nasal sac. In all the _Chromides_ the lateral line is incomplete or interrupted, and the scales are usually large and ctenoid. =The Cichlidæ.=—The suborder _Chromides_ includes two families, _Cichlidæ_, and _Pomacentridæ_. The _Cichlidæ_ are fresh-water fishes of the tropics, characterized by the presence of three to ten spines in the anal fin. In size, color, appearance, habits, and food value they bear a striking resemblance to the fresh-water sunfishes, or _Centrarchidæ_, of the eastern United States. This resemblance is one of analogy only, for in structure the _Cichlidæ_ have no more in common with the _Centrarchidæ_ than with other families of perch or bass. The numerous species of _Cichlidæ_ are confined to tropical America and to corresponding districts in Africa and western Asia. _Tilapia nilotica_ abounds in the Nile. _Tilapia galilæa_ is found in the river Jordan and the Lake of Galilee. This species is supposed to form part of the great draught of fishes recorded in the Gospels, and a black spot on the side is held to commemorate the touch of Simon Peter. Numerous other species of _Cichlidæ_, large and small, abound in central Africa, even in the salt ditches of the Sahara.