676 



SKELETON. 



of the dorsal fin, since they are denizens of 

 the world of waters. The tribe of fishes 

 known as Pleuronectidae is bordered dorsad 

 as well as ventrad by the locomotive palm- 

 organs, and therefore they simulate the series 

 of Jig. 49-k more closely than any other class 

 of animals. The Pletironectidse are the most 

 archetypal class of animals in Nature ; for the 

 first step of the law of formation in the meta- 

 morphosis of Jig. 494. is to create a cephalic 

 end (figA92.) and a caudal end (fig. 493.) to 

 this series of whole quantities, by a modifica- 

 tion of a certain number of the archetypes at 

 either end ; and thus the animal of the class 

 Pieuronectidae is fashioned, having the con- 

 tinuous palmed or fin-organ still persisting 

 dorsad and ventrad on those spinal arche- 

 types which stand in series between the 

 cephalic and caudal extremes. 



The structural composition of the head 

 will vary according to the number of those 

 serial archetypes which suffer metamorphosis 

 for its creation. For if we suppose that the 

 six quantities which are included within the 

 circle Q. c R (fig. 494.) should be subjected to 

 cephalic metamorphosis, we still can assign 

 no reason why Nature should limit herself to 

 the number si.v, or any other number, if ne- 

 cessity required the metamorphosis of a greater 

 number for one species of cephalic apparatus 

 and a less number for another. Although in 

 a former place I have numbered six segments 

 as proper to the composition of the human 

 head, still I am by no means of opinion that 

 Nature limits herself to number six in the 

 creation of all other species of cephalic appa- 

 ratus ; on the contrary, I shall not hesitate 

 to assert it as a fact, that (fig- 49^.) the head 

 of the plaice may be taken as an instance in 

 which fourteen dorso-ventral archet\'pes have 

 suffered cephalic modification.* 



The alternate fin-organs at the back and 

 venter occur by the alternate metamorphosis 

 of certain members of the palms of the conti- 

 nuous series of archetypal quantities. In the 

 Pleuronectidse, the dorsal and ventral palmed 

 fins are continuous for the entire length of 

 the spinal axis, as in fig. 494. ; but in other 

 classes of fishes we find the fins occurring 

 isolated at certain regions of the spinal axis : 

 such, for example, as the fins called dorsal, 

 jugular, abdominal, anal, and caudal; and this 

 alternation may be explained by referring to 

 fig. 494. If the palms which I have included 

 in the semicircles K i., M N happen to be 

 metamorphosed or subtracted, then the iso- 

 lated dorsal fin (M o L) will remain as we 

 find it presenting in many of the class Pisces, 

 and even in some of the cetaceans. The fin- 



* Professor Owen enumerates four vertebral seg- 

 ments as composing the heads of all aiiimals of the 

 four classes. For my own part, I see, no reason to 

 entertain the opinion that Nature limits herself to a 

 fixed number in the segments of the head, any 

 more than she does in constructing the cervix, the 

 thorax the loins, the sacrum, or the caudal region 

 of the spinal axes. Cams and Oken speak of the 

 number five, as though Nature limited the operation 

 of her law in patronage to this magical quinque in 

 vertebrate creation. 



organ is composed in all cases of a plural 

 number of palms; the number always corre- 

 sponding to the dorsal rays of the archetypes. 

 The palm is a hand, while the fin presents as 

 a series of hands. 



When the series of archetypal quantities 

 suffers metamorphosis at certain lines which 

 the creative hand of Nature draws through it, 

 the animal design or species is struck out 

 accordingly. When all quantity lying external 

 to the converging lines o i>, P D undergoes 

 metamorphosis or subtraction, then the series 

 of quantities which happens within these lines 

 will exhibit the condition of proportional and 

 progressional quantities, such as we find 

 standing in the caudal region of many animals. 

 When Nature draws the right line A B through 

 this region of the serial archetypes, and at the 

 same time metamorphoses all quantity above 

 or dorsad to this line, she creates the dorsal 

 region of the spinal axis of all terrestrial 

 animals, to which are remaining those parts 

 which we name the neural arches, sufficient 

 for the protection of the spinal cord. 



The quantity which occurs within the lines 

 A B, F G answers to the thoracic ophidian 

 skeletal axis, whose ventral or opposite costal 

 arches occur by a bicleavage of the azygos 

 ventral rays. The thoracic series of each 

 skeletal axis is formed after the same manner 

 as that of the ophidian. The numerical 

 length of every thorax varies according to the 

 number of those serial archetypes of fig. 494. 

 which suffers thoracic metamorphosis ; and 

 its position in spinal series varies also ac- 

 cording to the numerical position of those 

 archetypes which undergo a thoracic modifi- 

 cation ; for if they be the segments which 

 hold serial order between that which numbers 

 (in fig. 494.) as 13, and that which numbers 30, 

 then the thoracic length will correspond to 

 these numerical segments. 



When the head is fashioned of the six 

 quantities included in the circle Q c R, while 

 the neck is proportioned by the line E D, from 

 six, or seven, or more of those quantities 

 which succeed the head, viz. those segments 

 between 7 and 14, 15, or 16, then the neck 

 will number accordingly; and when the thorax 

 is to succeed the cervix, then the twelve or 

 more segments which succeed those of the 

 cervix are proportioned thoracically by the 

 lines F G. When, lastly, the lumbar, sacral, 

 anil caudal regions are to succeed the thorax, 

 it is the line F D which gives to these regions 

 their several quantitative characters. 



The law of " unity in variety" appears 

 therefore to be plainly demonstrable as an 

 archetypal plus series of quantities, undergoing 

 a graduated metamorphosis ; and if, by the 

 order of the foregoing remarks, I have left 

 upon the reader's mind the idea that the pro- 

 portional variety constitutes the species of one 

 form of skeleton compared to another, and to 

 all others of the four classes of vertebrate 

 animals, then my object has been attained by 

 the course of argument which 1 have pursued. 



(Joseph Maclise.) 



