674 



SKELETON. 



a nucleus, around which are arranged, in pal- 

 mate order, the rays of nine archetypes, which, 

 bending towards each other, and to the hori- 



zontal ray (9), fashion the fan-shaped caudal fin. 

 This caudal fin, whose rays describe the arc 

 p Q, is composed of the palms of nine arche- 



Fig. 492. 



Tl\e cranio-Jacial apparatus of the osseous fish (Phuronectid<e), 

 Indicating the metamorphosis of twelve or more spinal quantities in its composition. 



types, radiating from the common centre (a). 

 The nine inferior palms are those which num- 

 ber from 17 to the palm 9 ; and the nine supe- 

 rior palms are those which number from 1 to 

 the palm 9 ; while the azygos palm 9 may be 

 regarded as composed of the dorsal and ven- 

 tral palms of the last archetype bent towards 

 each other, and becoming in the horizontal 

 line fused together. The bones (o, p, q\ are 

 the counterparts of the neural and haemal 

 laminar arches, assuming the same palmate 

 order as the palms. The head (Jig. 492.) and 

 the caudex (Jig. 493.) constitute the origin 

 and termination of spinal series, and are ex- 

 amples of special modifications exercised upon 

 the original archetypal quantities. 



PROP. XLVI. The uniform archetypal se- 

 ries undergoes a graduated metamorphosis of its 

 quantities far the production of all varieties of 

 skeletal species. In _/?,. 494. I represent the 

 archetypal series of the dorso-ventral quanti- 

 ties constituting the uniformity, forasmuch as 

 all the segments are plus and quantitatively 

 equal. The segment 1 is equal to the segment 

 38, and to all the intervening segments. 

 This uniform series of quantities appears 

 finite, like the right line (CD) which passes 

 through its centre; but as the right line itself 



is but a part or proportional of that ideal line 

 which is infinite or boundless, so of the series 

 of archetypal quantities, numbering in the 

 figure from 1 to 38 ; for this series may like 

 number be produced to infinity in imagina- 

 tion. 



In the serial line (Jig. 494.) which is com- 

 posed of 38 archetypal dorso-ventral quanti- 

 ties, we do not as yet distinguish any special 

 differences ; and this is owing to the fact that 

 all the quantities composing the series are simi- 

 lar or homologous ; neither can we discover 

 any reason why we should name either of the 

 extremes of this serial line (D c) as the origin 

 or the termination in preference to the other 

 extreme, for the segment 38 is equal to the 

 segment 1 ;| and hence it matters nothing to 

 the entities themselves at which end of the 

 series we commence the enumeration. In 

 nature there is no instance of a skeletal axis 

 constituted of such a uniform serial line of 

 quantities as those of Jig. 494., but yet it is 

 possible to prove that every skeletal axis is 

 part of such an original series. That skeletal 

 axis which approaches nearest to the abso- 

 lutely uniform condition of Jig. 494. is to be 

 found amongst the class Pisces. 



The skeletal fabrics of all animals are sym- 



