40 RECORDS OF THE AUSTRALIAN MUSEUM. 



and direction of its companion. Groode and Bean write": — ^"The 

 large fan-shaped ventrals are used as support in resting on the 

 bottom, and in swimming they are generally closed in their groove 

 unless the fish is moving leisurely, when they may be partly 

 expanded." If the ventrals are fully operative only when the 

 fish is resting on the bottom they can, considering the truly pelagic 

 habit, be of little service. In the Sargossa sea, where the species 

 abounds, a resting-place would be afforded by the weed, but else- 

 where, the coasts excepted, no support would be encountered. As 

 the ventral fin of Nomeus by its large size is perhaps the most 

 striking character of the fish, it must have a more important 

 function than an adaptation to a condition in which it would, by 

 the remotest chance, find itself. 



That the fish should extend its fins when on the bottom of a 

 roclc-pool can only be regarded as an unnatural attitude, such as 

 a caged animal might assume, the fish not previously having en- 

 countered bar to its downward progress. 



The relationship which exists between Nomeus and Physalia is 

 a very curious one, and invites speculation as to tlie advantage of 

 the association. A similar partnership is known between Fishes 

 and Medusaj. The benefit must primarily be with the fish, for it 

 is a voluntary agent, whereas the Pliysalia has no power of 

 locomotion. If the fish secures safety from its enemies by enter- 

 ing the area embraced by the deadly tentacles of the Physalia, 

 which attain a length of ten to twelve feet, it must be immune 

 to their influence; a remarkable condition considering that, as I 

 have previously recorded, small fish have often been seen in their 

 stomachs and entangled in their tentacles.^ 



Garman^ seems to con.sider that there is no such immunity: — 

 " On several occasions Physalia; have been taken with partially 

 digested Nomei in their grasp, which would indicate that the little 

 fishes were sometimes preyed upon by the 'men of- war.'" 



It has yet to be shown that the partially digested Nomei were 

 not ejected by other fishes before entering the grasp [tentacles] of 

 the Physalia, digestion being performed by the stomach and not 

 by the tentacles. 



Goode and Bean, in the work already (juoted, inform us that 

 ten individuals were taken in a dip-net, from the deck of the 

 "Albatross," off the Florida coast, all swimming under one 

 Portugue.se Man-of-war. 



It is probable that, in addition to protection, the fish derives 

 its food from association with the Pliysalia much as does the 

 Remora in accompanying a Shark. The Pliysalia doubtless 



7 Goode and Bean— U.S. Nat. Mus., Bull. Oceanic Ichth., 1895, p. 220. 

 s Waits— Aust. Mus. Mem , iv., 1, Fishes, 189'.), p. 1-5. 

 y Garman — Bull. Lab. Nat. Sci. Iowa, 1896, p. 81. 



