SUBKINODOM METAZOA. 43 



tiou, but in organ-individuals reproduction of the constitu- 

 ent cell-individuals is not necessarily connected with the 

 reproduction of the entire individual, but may simply increase 

 the number of lower-grade individuals of which it is com- 

 posed. Similarly multiplication of the organ-individuals of a 

 metamere, or of the metamere-individuals of a cormus may 

 occur without producing reproduction of the whole ; it is 

 simply growth. From growth to reproduction by budding 

 the path is short, and various intermediate stages connecting 

 the two processes can be found. Hence reproduction has been 

 aptly defined as "discontinuous growth," though perhaps it 

 would be even more apt to define growth as reprodttction with- 

 out discontinuity, growth in a Metazoon depending on the 

 reproduction of the lower-grade individuals of which it is 

 composed. 



It is possible to carry this idea still farther back and refer the growth 

 of a cell to the reproduction of the constituent elements, plasomes, of which, 

 it may be imagined, it is composed. In the simplest cells the various 

 forms of plasomes are distributed throughout the cell, but in the higher 

 Protozoa, for instance, an aggregation of similar plasomes occurs, giving 

 rise to such structures as the myophanes. In a similar manner in the 

 lower Metazoa, although a division of labor and structural differentiation 

 has taken place among the constituent cells, yet the cells possessing similar 

 functions, as, for instance, the nerve-cells, are more or less irregularly 

 scattered throughout the body, only becoming aggregated, in the higher 

 forms into distinct tissues, and giving rise to the most .perfect type of an 

 organ-individual. Likewise in a metamere-individual a multiplication of 

 the organs leads to a transition form with discretely arranged parts, the 

 definite aggregation of which produces a cormus, composed in the simpler 

 forms of distinct metameres, which become more and more integrated and 

 subordinated to the individuality of the cormus in higher types of that 

 grade of individual. 



According to this view the segmentation or metamerism of the higher 

 Metazoa is the result of the multiplication and subsequent integration of 

 the organ-individuals of an ancestral metamere-individual, and explains 

 the occurrence of imperfect metamerism in certain forms of that grade of 

 individuality (Turbellaria). Some authors have considered metamerism to 

 have arisen by the reproduction by budding of an ancestral metamere, an 

 idea which fails to explain satisfactorily the condition just referred to. 

 The view presented here considers metamerism to be the result of growth. 

 It has not arisen by the reproduction of the metamere, but by that of its 

 organs, just as a typical organ-individual has arisen by the reproduction 

 and integration of its constituent cell-individuals. 



