208 Comparative Physiology. 



circular and longitudinal motion. When the axis is not deve- 

 loped therefore by the latter, the former or circular prevails. 

 In the lower animals the circular and spiral symmetry prevails. 

 In Articulata (insects) the hi-lateral symmetry is carried to its 

 greatest extent, the locomotive powers being developed to their 

 highest extent. In Mollusca the locomotive organs are adapted 

 only for slow and feeble progression ; and the niitritive appa- 

 ratus constitutes almost the entire bulk of the body, and there is 

 a general want of lateral symmetry. In Vertebrata the uni- 

 formity of the two sides is only external, the nutritive organs 

 apparently being developed internally on an asymmetrical 

 plan." 



The fascicled appearance of the leaves of pines, the whorled 

 leaves of many plants, and the circular arrangement of the parts 

 in flowers, have been termed abortive, from the greater part of 

 the branch, called the axis, being wanting. The doctrine has been 

 carried so far as to call the parts of a flower mutilated leaves. To 

 a certain extent the doctrine is true, as we frequently see a branch 

 developed from the centre of a flower ; perhaps, however, we are 

 not warranted to call every departure from a former to a new 

 mode of developement abortion, because parts of the one are want- 

 ing to the other. The power which gives the longitudinal or ver- 

 tical developement to plants is always found associated with the 

 radiated or circular, as in the medullary rays of Exogens, and the 

 circular joints of Endogens. It is found to prevail most in the 

 higher classes of plants, and, united to the circular, to cause 

 the spiral arrangement of the leaves on the branches ; but, 

 though in the flower the circular developement overcomes in 

 many instances the vertical, it does not follow that it is by 

 abortion ; it is the way in which flowers normally develope, and 

 we cannot say that it would have been more perfect to elon- 

 gate. It is also repugnant to our ideas of flowers being con- 

 cerned in the highest function of reproduction, to have them 

 denominated abortions or mutilations. Transformation would 

 be a better term, as it would really seem from stamens and 

 pistils becoming petals, and petals becoming partly or wholly 

 leaves, that they are undoubtedly convertible forms, according 

 to the nature of . their food and other circumstances they are 

 placed in. Abortion would be more properly confined to such 

 instances as interfere with the normal number of parts, as in 

 stamens, petals, &C.5 when wanting ; and mutilation or de- 

 generation to parts more obviously deformed from their not 

 being developed in the usual manner, as in full flowers, &c., 

 where deformity and dejaarture from the normal mode appear 

 more connected than in the higher developement of a flower from 

 a leaf bud ; deformity not being so applicable to a departure from 

 a lower to a higher function as the reverse. This has been 



