228 



EXPLANATION 



the work of Agassi z, I deemed myself safe in trusting to 



the report of this industrious inquirer and ingenious 

 writer, whose volume was then newly published. How 

 recent the contradiction of the once-supposed affinity 

 may be, or what faith to place in it, I know not ; but the 

 reader will probably hold one who only pretends, in this 

 instance, to the character of a general writer, excused, 

 when he shows so distinguished an expositor of phys- 

 iology as Dr. Carpenter still more recently countenan- 

 cing the idea : — " The bodies of fishes," says he, " are 

 usually covered with scales or plates, which have some- 

 times a bony hardness, and which, in some species of 

 fish that do not now 7 exist alive, appear to have been of 

 the density of enamel. Thus we have a sort of transition 

 to the external skeletons of the invertebrated animals ; 

 and in this class, also, we not unfrequently find the in- 

 ternal skeleton so deficient in the stony matter from 

 which bone derives its hardness, that it seems like car- 

 tilage or gristle ; and in a few of the lowest species, we 

 do not even find a distinct vertebral column ; so that the 

 change of character from the vertebrated to the inverte- 

 brated series is a gradual, and not an abrupt one, and 

 would probably be found still more gradual, if we were 

 acquainted, not only with all the forms of animal life 

 which now exist, but also those which have existed in 

 ages long gone by, and are now extinct." 



The above argument relates to the general fact of the 

 first fishes being placoidean. It is necessary, also, to 

 meet the inquiry why there should be no fossil remains 

 indicating a transition from the lower animals to fish. 

 The reviewer speaks of a recently discovered cestraceon 

 below any other fish-beds in England. '* Such," he ex- 

 claims, "are nature's first abortive efforts." "We en- 

 treat," he adds, " any good naturalist well to consider 

 such facts as these, and tell us whether they do not 

 utterly demolish every attempt to derive such organic 

 structures from any inferior class of animal life found in 



is more elongated, but both possess the crescent-shaped head, and 

 Doth the angular and apparently jointed body. They illustrate ad- 

 mirably how two distinct orders may meet. They exhibit the 

 joints, if T may so speak, at which the plated fish is linked to the 

 shelled crustacean. Now the coccosteus is a stage further on ; it 

 is more unequivocally a fish ; it is a cephalaspis,with a scale-covered 

 tail attached to the angular body, and the horns of the crescent 

 shaped head cut off." — Old Red Sandstone, p. 54. 



