192 SMITHSONIAN MISCELLANEOUS COLLECTIONS [VOL. 50 



VI 



The newly hatched larvae are about a sixth to a quarter of an inch 

 (4-6 mm.) long or a little more. "They are tadpole-like — with 

 the remains of yolk, the oil-globule, occupying the right side, while 

 the marginal fin is continuous, dorsally and ventrally. The caudal 

 has only embryonic rays, and there is a thickening (hypural) be- 

 neath the notochord in this region. The short breast-fins show in- 

 dications of true rays. The circulation in the vessels of the yolk- 

 sac goes on in jerks, so 

 different from the con- 

 P^HH tinuous rapid currents in 



_, „ T _ . . , the arteries of the tail and 



hie. 44. — Young Lumpnsh j. mm. 111 length. ^ 



After A. Agassiz. other P arts - The dorSal 



aorta bends downward 



just within the tip of the notochord. The young Lumpsuckers 

 swim very actively by rapid vibrations of the tail and the 

 pectorals. The heavy anterior end of the body is thus favorable for 

 progression." Such were the larva? obtained by Mcintosh and Mas- 

 terman in early May. "By the 12th day the fish has increased con- 

 siderably in bulk, and measures 6.75 mm." ; the yolk has disappeared, 

 the fins become differentiated, the two dorsals especially showing dis- 

 tinct rays; the anal, however, though rayed, is "joined to the caudal 

 by a strip of larval fin without rays ;" and the caudal is still heter- 

 ocercal. 



From this earliest stage with the continuous fin round the long 

 postanal region there is a regular development into the adult stage. 



Fig. 45. — Young Lumpnsh 10 mm. Fig. 46. — Young Lumpfish 20 mm. 



long. After A. Agassiz. long. After A. Agassiz. 



The tail end becomes abbreviated and concentrated ; a division 

 ensues between the caudal, dorsal, and anal fins ; the heterocercy 

 diminishes and is at length replaced by the homocercal tail ; the first 

 dorsal, originating in a protuberance which becomes quite upraised, 

 finally becomes distinctly developed, and lastly the dermal ap- 

 pendages are developed, the lateral tubercles extending from the 



