76 



NATURE 



[March 17, 192 1 



New Studies of Sun-fishes made during the "Dana" Expedition, 1920. 

 By Dr. Johs. Schmidt, Carlsberg Laboratory, Copenhagen. 



[The Dana is a " four-masted motor schooner of 

 550 tons, belonging to the East Asiatic Company of 

 Copenhagen. His Excellency H. N. Andersen, direc- 

 tor of the company, generously placed this vessel at 

 the disposal of the Danish Committee for the Study 

 of the Sea for a cruise in the Atlantic] 



THE sun-fishes (Mola and Ranzania) are un- 

 doubtedly among- the most remarkable 

 creatures which inhabit the oceans. By their 

 peculiar shape, altogether unlike what we are 

 accustomed to find in fishes (Figs. 1-3), their 

 divergence in point of internal structure, and the 

 considerable size which the best-known species 

 attains, they have from ancient times attracted 

 the attention of naturalists. 



Fig. I.— The s/iori sun-fish {Moia roiuK'/a). Length, a-ii metres ; weight 

 not noted, probably about 500 kilos. (From Murray and Hjort's 

 'Depths of the Ocean.") 



Two species were known with certainty to occur 

 in the North Atlantic : the short sun-fish (Mola 

 rotunda, Fig. i) and the ohlong sun-fish (JRan- 

 zania truncata, Fig. 2). To these I am now able 

 to add a third: Mola lanceolata {Fig. 3), a form 

 the specific value of which has been questioned 

 by recent authors. Though related to Mola 

 rotunda, it is doubtless a distinct species, differing 

 by the pointed tail and the number of fin-rays, 

 as well as by several larval characters. 



The oblong sun-fish attains a length of only 

 two or three feet ; the short sun-fish, on the other 

 hand, is known to have reached a length of eight 

 to ten feet or more, and a weight of more than a 

 ton. It is thus one of the giants of the ocean. 

 That the sun-fishes also possess gigantic strength 

 is evident from a report of one of the Prince of 

 NO. 2681, VOL. 107] 



Monaco's cruises in the Atlantic with the yacht 

 Hirondelle, where we read that a large specimen 

 — the same as that represented in Fig. 3 — which 

 was harpooned from a boat sent out from the 

 yacht, almost pulled the boat under in its struggles 



Fit. 



-The ohlonf sun-fish {Ranzania truncata). Length, 

 0*65 metre. (Krom Beauregard.) 



to escape. The sun-fish owes its strength to the 

 powerful development of. the muscles controlling 

 the two large vertical fins (the dorsal and anal, 

 shown in Fig. i). On the other hand, the muscles 

 generally composing the greater part of the body 



Fig. 3. — Mola lanceolata, a .species related to the short sun-fish, but diflfer- 

 ing by the pointed tail. Length, 2 metres; weight, 285 kilos. (From 

 the Prince of Monaco.) 



in a fish, the great lateral muscles, are rudi- 

 mentary in the sun-fish. 



The short sun-fish [Mola rotunda) occurs com- 

 paratively frequently ®ff the coasts of Western 

 and Northern Europe, near the British Isles more 



