Chap. VI. ANNELIDE PAEASITIC IN LEPAS. 45 



There was above each of the lateral tufts of bristles a 

 branchia, simple on a few of the foremost segments, and 

 then strongly arborescent to the end of the body. The 

 animal, a female filled with ova, evidently, from these 

 characters, belongs to the family of the Amphinomidse ; 

 the only family the members of which, being excellent 

 swimmers, live in the open sea. 



That this animal had not strayed accidentally into 

 the Lepas, but appertained to it as a regular and per- 

 manent guest, is evidenced by its considerable size in 

 proportion to the narrow entrance of the test of the 

 Lejoas, by the complete absence of the iridescence which 

 usually distinguishes the skin of free Annelides and 

 especially of the Amphinomidse, by the formation and 

 position of the inferior setae, &c. But that a worm be- 

 longing to this particular family Amphinomidae living 

 in the high sea, occurs as a guest in the Lejpas, which 

 also floats in the sea attached to wood, &c., is at once 

 intelligible from the stand-point of the Darwinian theory, 

 whilst the relationship of this parasite to the free-living 

 worms of the open sea remains perfectly unintelligible 

 under the supposition that it was independently created 

 for dwelling in the Lejpas. 



But however favourable the examples hitherto re- 

 ferred to may be for Darwin, the objection may be 

 raised against them, and that with perfect justice, that 

 they are only isolated facts, which, when the considera- 

 tions founded upon them are carried far beyond what 

 is immediately given, may only too easily lead us from 

 the right path, with the deceptive glimmer of an ignis 



