OP ARTS AND SCIENCES. 73 



face of the water ; but, when disturbed, move very rapidly about 

 through the water. In this stage, we can notice the first trace of the 

 ventrals, at the anterior part of the ventral embryonic fold. They 

 appear first as minute swellings on each side of this fold, and they con- 

 sist of a central shaft with a fleshy fringe like the pectorals. Seen 

 from above (Plate III. fig. 32), the head has become elongated, the 

 sucking-disk is reduced to a single row of small suckers, and we now 

 begin to see what becomes of this organ. The fleshy globular termi- 

 nation of the upper jaw of the adult Lepidosteus is the remnant of 

 this embryonic sucking-disk. The coloring of the young fish is be- 

 coming more and more like that of the adult ; the dorsal region is 

 mottled with broad irregular patches of brown ; a strong black line 

 extends from behind the eye, on the lower side of the median line, to 

 the extremity of the tail. The young already have also the peculiar 

 habit of the adult of coming to the surface to swallow air. When they 

 go through the process under water of discharging air again, they open 

 their jaws wide, and spread their gill-cover, and swallow as if they 

 were choking, making violent efforts, until a minute bubble of air has 

 become liberated, when they remain quiet again. The resemblance to 

 a Sturgeon in the general appearance of this stage of the young Lepi- 

 dosteus (Plate III. fig. 30) is quite marked. 



The growth of the young Lepidosteus is very rapid. Hatched the 

 28 th of May, they had on the 14th of June attained a length of three- 

 quarters of an inch (Plate III. fig. 33). The snout has become greatly 

 elongated ; and the upper jaw shows plainly that the sucking-disk is 

 to become the fleshy accretion at the extremity of the snout. The 

 embryonic fin-fold has become slightly indented, indicating the posi- 

 tions of the future dorsal and anal fins. The ventrals have increased 

 somewhat in size. In this stage, we see the first trace of the permanent 

 fin-rays, of the dorsal, caudal, and anal fins. There are also most 

 delicate embryonic fin-rays, just as we find them in bony fishes at cor- 

 responding stages. The fringe of the pectorals is incessantly in rapid 

 vibration, as well as the tip of the tail, except when the fish is at rest 

 near the surface of the water. The tail does not necessarily vibrate 

 with the pectorals : either may be in motion without affecting the other. 

 The teeth make their appearance in this stage, and there are a few 

 fin-rays in the fringe of the pectorals. 



Seen from above, the pectorals are usually carried at right angles 

 to the body when in rapid motion (Plate IV. fig. 34). Our young 

 Lepidosteus has now reached a stage (Plate IV. fig. 36) very similar 

 to that first described by Professor Wilder. The head, when seen from 



