164 AFFINITIES AND GEOGRAPHICAL 



with numerous small teeth, by which they fasten upon living 

 animals for sustenance. The affinity to the cephalopods is 

 fully admitted. It is seen in the nature of the skeleton, so 

 like that of the belemnite, in the character of the investing 

 skin which ejects a copious secretion whenever the animal 

 considers itself in danger, in the power of respiring through 

 the gill apertures without any dependence for that function 

 on the mouth, and in the eight free filaments seen in some 

 species extending forward from around the mouth," repre- 

 senting," as Professor Owen remarks, " the eight ordinary 

 arms of the Cephalopoda Dibranchiata, but arrested in their 

 development by reason of the preponderating size of the caudal 

 extremity of the body, which now [that is, in the fish] forms 

 the sole organ of locomotion." The lancelot, one of this 

 family, is so extremely humble in organization, that Pallas 

 mistook it for a limax (a gasteropodous mollusk), and it has 

 only of late been finally established among the fishes. Some 

 difficulty has been experienced in seeing true affinity between 

 the bag-like figure of the mollusk and the cylindrical elon- 

 gated form of the fish ; but it has been suggested that the mol- 

 lusk is, as it were, the fish doubled in or inverted upon itself: 

 hence the end of the alimentary canal so near to the mouth. 

 The inversion reversed or undone, makes the fish. These 

 appearances of propinquity are most arresting. If they do 

 not indicate genealogical connexion, how should we account 

 for them ? On any other supposition, how should such 

 peculiarities of organization be seen exactly at this point in 

 the animal scale? The fishes here spoken of are not dis- 

 covered in a fossil state. For this their want of hard parts 

 unfitted them ; but they are classed with the Chondroptergii, 

 or cartilaginous fishes, which, we have seen, are amongst the 

 first found in the ascending series of rocks. The affinity and 

 the geological succession, are therefore in perfect harmony. 

 It is here important to remark the progress from entirely soft 

 animals, to an order bearing cartilaginous plates to protect a 

 rudimental brain ; from these, again, to an order having a 

 skull and vertebral column of cartilage ; a series of advances 

 entirely conformable to phenomena seen in individual deve- 



