FIG. 23.—Alligator-gar, _Lepisosteus tristœchus_ (Bloch). Cuba. ] The great alligator-gar, _Lepisosteus tristœchus_, reaches a length of twenty feet or more, and is a notable inhabitant of the streams about the Gulf of Mexico. Its snout is broad and relatively wide, and its teeth are very strong. It is very destructive to all sorts of food-fishes. Its flesh is worthless, and its enameled scales resist a spear or sometimes even shot. It breathes air to a certain extent by its lungs, but soon dies in foul water, not having the tenacity of life seen in _Amia_. =Embryology of the Garpike.=—Mr. Alexander Agassiz has given an account of the embryology of the garpike, of which the following is an abstract: "The garpike comes up the St. Lawrence in May, lays its eggs about the 20th, and then disappears. The eggs are large, viscous, stick fast in an isolated way to whatever they fall upon, and look much like those of toads, having a large outer membrane and a small yolk. Artificial fecundation failed, but about 500 naturally-laid eggs were secured, of which all but 30 perished through mold. The young began to hatch in six days. Out of 30 young hatched, 27 lived until the 15th of July. Connection with the sharks appears in the similarity of the branchial arches and by the presence of the lateral fold in which the pectoral fins are formed; the way the tail is developed is very like that of the bony fishes. Among the Ganoids it appears, as well as in ordinary fishes, the dorsal cord is straight at first, then assumes a slightly upward curve at the extremity, when finally there appears the beginning of a lobe underneath, pointing to a complete heterocercal tail. All this is as in the bony fishes, but this is the permanent condition of the garpike, while in the bony fishes the extremity of the dorsal cord becomes extinct. The mode of development of the pectoral lobe (very large in this species) furnishes another resemblance. In the brain, and in the mode of formation of the gills, a likeness to the sharks is noticeable. The young garpikes move very slowly, and seem to float quietly, save an exceedingly rapid vibration of the pectorals and the tip of the tail. They do not swim about much, but attach themselves to fixed objects by an extraordinary horseshoe-shaped ring of sucker-appendages about the mouth. These appendages remain even after the snout has become so extended that the ultimate shape is hinted at; and furthermore, it is a remnant of this feature that forms the fleshy bulb at the end of the snout in the adult. The investigations thus far show that the young garpike has many characteristics in common with the sharks and skates, but it is not so different from the bony fishes as has been supposed."