LUCERNARI.E AND THEIRAL LIES. 3 



give utterance to the woxtX pold.rilij. This i.s the dominant, main idea of sentient 

 life. 



6. It is •polariiy which is evinced when the self-dispersing, self-repellant poten- 

 tiality of the animal-egg lays down the right and left of the germ on opposing 

 sides of a line ; when the cephalic and caudal areas grow in opposite directions 

 from a common point of emanation ; or when the animal and vegetative founda- 

 tions project themselves into diametrically diverse, dorsal and ventral spaces. 

 Each and all of these phenomena have a common point to rest upon ; and they 

 proclaim, by their mode of operation, the controlling influence of a power which, 

 fixing itself upon that point, as it were, radiates itself through the whole organism, 

 and disposes its several features in such a way that they all display, either in mode 

 of evolution or by a direct connection, a polar tendency ; a growing out of one 

 pole and a dispersion toward the opposite one ; features most developed and 

 decided in configuration next the point of departure, and least developed and most 

 diff"use and indeterminate in the opposite area ; the latter always through life 

 standing in the same relation to the former as supply does to demand, as nutrition 

 does to the power which regulates the absorption of the nutriment. 



7. But h'daieralihj carries with it something more than the mere dextral and 

 sinistral opposition of the lateral halves of the body ; it is not merely the biparti- 

 tion of a unit of form ; for the distal as well as the proximal edges of these halves — 

 the free borders and the margins of contact — are mutually interchangeable ; the 

 former may take the place of the latter, and yet leave the apparent bipartite unit 

 undisturbed in internal relations. 



8. Anlero-posteriority exhibits the same intcrchangeability as bilaterality, but, 

 although plainly enough, not so conspicuously in a comparative, homological sense 



'as in the physiological interplay of the functions, such as we see in the relations 

 of the allantois to respiration in the embryo, or in the ratio of excretion of the 

 renal organs dependent upon the degree of activity of the respiratory and perspi- 

 ratory functions ; or in the relation of the reproductive organs to the vocal and 

 respiratory, when the former are in an abnormal condition, or when they change 

 from one period of Hie to another, from youth to adolescence ; and in many other 

 interdependent relations familiar to the morphologist of the present day. 



9. Bilaterality, antero-posteriority, and dorso-ventrality, the three principal suh- 

 dominanfs of polarity, have a very methodical disposition, and are quite pronounced 

 and sharply defined among the higher groups of animals — the more seemingly 

 units of organization — but if we go to the opposite extreme of grade we shall find 

 among the lower classes of life, that the polaric element (like the differentiation 

 of organization, and that of function) is in an almost elementary condition, 

 expressing itself vaguely in the scattered heads of a branch of Coryne, or Tubu- 

 laria, or Clavellina ; or a little more determinately in the distichous arrangement 

 of the hydra heads of Dynamena and Sertularia, or in the singularly stellate 

 disposition of the zooids of Botryllus, witli their common cloacal orifice. 



10. When, however, polymerism, in its iisually accepted sense, fails, as it daes 

 step by step in the gradually rising degrees of rank, polarity gains the ascendency 

 in point of regularity and the closer intimacy and symmetrical arrangement of the 



