into the fesiiiratiii-y Iitc, until (inly the t'nrc|);ii-t i-cin;iins 

 oiitsiik'. TIk' fish iKiw cntii-i'lN" enters the IhkK' of tlie 

 se;i-ctieiiiiil)cr by means of a few puweflnl, nnihiiating 

 Hiovemetits. Now and then it pw'jis out to l)reatiie. to 

 .seize some small ei'ustaeean that has come too neaf, 

 or to e\aeinite the contents of its intestine tin'oiijrh 

 the \ent, wiiieli is sitiuitetl far forwai-ii. The lish must 

 also, in all prolialiility, leave its place of refnye and 

 lead an inde|ienilent life during the s|iawninii-season. 

 After liie lirst fish a second, a third, or even a seventh 

 ma\' take up its abode in the same sea-cueiind)er. One 

 Ficroffer seems ^^cnerall}' to ilo no harm to the sea- 

 ciicumlier; but if several come, it dies after ejecting' 

 its entrails, and the lish pce|j out from the empty skin. 

 Thus, the Fierasfer lives originally in the ramified 

 breathing dnet (resi)iratory tree) of the sea-cucumber; 

 but b\- the l)ursting of the walls of this duct it easily 

 gains a passage into the large cavity of the body, 

 where it is fre([nenth- found. Some species of the ge- 

 nus lead a similar life in the body cavity of the Indian 

 trejiangs, and in all |)robabilit\- gain entrance in the 

 same manner; but the Fierasfers that live within the 

 boih of the large starfishes (genus Culcifa), must cer- 

 lainh' pass through the mouth, for in these animals 

 there is no anal aperture (cloat'a) to admit of the pas- 

 sage of any fish. 



F,\en though these fishes may derive some nonrish- 

 meiit from the fluids in the l)odv of the sea-encumber 

 in -which they live, still tiiey are no true parasites, and 

 seek their food chiefly outside, thus being frequenth" 

 funid svvimming freely about. The case may be 

 different in the other genus of this subfamily, Eiiche- 

 linjiliis. which is a native of the waters round the Phi- 

 lipjiine Islands, and whose parasitic natiu'e seems to be 

 more pronounced and to ha\e involved the loss not 

 oidy of the ventral, but also of the pectoral fins. 



From the Gulf of Panama, on the west coast of 

 Central America", Pitxam has described a species, Fie- 

 rasfiT duliias, that iiospitates in pearl-mussels, be- 

 tween the mantle and the shell. Mere it leads a life 

 so (piiet and inoffensive that the mussel sometimes 

 succeeds in enveloping it in a layer of nacre. 



The weak sight possessed l)^• these fishes, at least 

 by daylight, is compensated by a special development of 

 the senses of touch and hearing. The system of the 



"IDS. 599 



l.'itei'al line (tig. Ill) in<'ludes large passages on the 

 head, from the snout round th<' eyes (the suborbital 

 and sujiraorbital branches), along the forehead and the 

 top of the head on each side to the temples, and from 

 the under surface of the lower jaw, along the margin 

 of the preoperculum, to the same spot, where the lateral 

 line proper begins. The two lateral halves of the sys- 

 tem ai'c tunted by transNcrse canals between the eyes 

 and between I hi' temples. The sensory organs lie in 

 hirge luimbei's along these canals as well as in a row 

 along each side of the back and in another denser row 

 along each side of the base of I he anal fin. The laby- 

 rinth is remarkable for its comparatively large otoliths. 

 The po\\ ers of hearing are probably strengthened — 

 and sounds perhaps jiroduced, though we haxe no ob- 

 servations on this head — ]iriiK-ipall\- by the comiexion 



Fig. 144. Ceplinlic system nf (lie lateral line ("muciferous canals") 



in Fierasfer dentatus. A. from above; D. from tlie left. 



After E>iEriv. 



(jiroliably common to all the ( tphidioids) between the 

 air-bladder, the first vertebra', and the base of the 

 occijiut. In the Cods we have seen an internal con- 

 nexion between the air-bladder and the transver.se 

 processes of the middle and posterior abdonunal verte- 

 lira'. Here this connexion is removed farther forward; 

 and the first four (or, as in Firrasfrr deiifahis, only 

 the first three) vertebra' with their ribs are mollified 

 aci'ordingh'. The first verteln-a is as usual closely 

 united to the occipital bone, the second is shortened. 

 The first two pairs of ribs retain a greater or less amount 

 of mobility, the third (and in Fierasfer acus even the 

 fourth) pair coalesces with the body of the vertebra 

 like ordinar\- transverse processes. In Fierasfer aciis 

 the third pair is so much enlarged that it coalesces 



" According to Put.vam (Proe. Soc. Nat. Hist. Boston, vol. XVI (1874), p. 343) '.lie same species inhabits iloloUmrians on the cast 

 coast of Central America, in Florida Bav. 



Scandinacian Fhlie. 



