CHAP. VJIL] LIKENESSES IN ANIMALS AND PLANTS. 273 



out to have been the right one; and a latent tendency 

 speculatively divined has now been made palpably evident. 

 Ho\v many other latent tendencies may not exist which 

 never render themselves visible ! Might it not be contended 

 that the ultimate segmentation of the bony cranium of 

 mammals is one mode of expression, disguised and highly 

 modified, of such latent earliest tendency to serial- seg 

 mentation ? 



But most striking of all recent phenomena concerning the 

 vertebral archetype is the return just made by Pro 

 fessor Huxley * to the conception so long ago advo- Amphioxus 

 cated by Professor Owen, that serial segmentation, however 

 latent and disguised, extended primitively and fundamentally 

 to quite the anterior end of the head. The first-named 

 Professor here advocates the view that we have an approxi 

 mation to the early form of the vertebrate skull in that very 

 exceptional little fish the Laneelet (Amphioxus), in which 

 the front end of the body is, like all the rest of it, made up 

 of a series of similar segments, although the part representing 

 the bodies of the vertebrae of higher animals is itself unseg- 

 mented. The general resemblance of the new concrete type 

 of Professor Huxley to the old type, as exhibited in the well- 



* See Proceedings of the Royal Society, No. 157, p. 127. The author s 

 determination of the homologiea he seeks to establish, rests upon the con 

 stancy of position of the velum palati which he has selected as Ms fixed point 

 A certain hesitation in assenting to the new view may be justified by the 

 absence ;as far as yet known) of the auditory organ in the Amphioxus If 

 there is one thing which is constant in the verfebrata it is the auditory 

 capsule, and the figures on the Paper referred to show it relatively largest in 

 the youngest condition of the Ammoc-setes chosen for comparison. The dis 

 tribution of the cranial nerves can hardly bo said to afford decisive characters 

 since as there are myotomes, if nerves are supplied to them laterally from a 

 central nervous trunk, each nerve must divide into a dorsal and a ventral 

 branch to supply each muscular segment. Similarly nervous supply must be 

 sent to the front end of the body ; and if the so-called eye spot of Amphioxus 

 be an eye-spot, the circumstance that this nerve passes over it, though a 

 striking fact, is scarcely sufficient to identify it with the ophthalmic divisfou of 

 the fifth nerve of fishes and higher vertebrates. 



The constantly increasing number of instances of the independent origin 

 of similar structures makes us think it far from impossible that vertebrate 

 genetic affinity may lie at least as much in the direction of the annelid worms 

 us in that of the ascidiuns, and that there are hardly as yet data to determine 

 which of the curious cross relationships exhibited by the Laneelet, are due to 

 genetic affinity, and which to homoplasy. 



