382 THE ZOOLOGIST. 



presume to express any opinion further than this, that the instances 

 I have cited show that there is much reason for further careful 

 observation by the field naturalist, and much yet to be discovered 

 by the physiologist and the chemist, as to the composition and 

 nature of animal pigments. 



I had proposed to occupy a considerable portion of my address 

 with a statement of the present position of the controversy on 

 heredity, by far the most difficult and important of all those 

 subjects which at present attract the attention of the biologist; 

 but an attack of illness has compelled me to abandon my purpose. 

 Not that I proposed to venture to express any opinions of my 

 own, for, with such protagonists in the field as Weismann, 

 Wallace, Romanes, and Poulton on the one side, and Herbert 

 Spencer and Hartog on the other, " Non nostrum inter vos tantas 

 componere lites." , 



So far as I can understand Weismann's theory, he assumes the 

 separation of germ cells and somatic cells, and that each germ cell 

 contains in its nucleus a number of " ids," each " id" representing 

 the personality of an ancestral member of the species, or of an ante- 

 cedent species. " The first multicellular organism was probably 

 a cluster of similar cells, but these units soon lost their original 

 homogeneity. As the result of mere relative position, some of the 

 cells were especially fitted to provide for the nutrition of the 

 colony, while others undertook the work of reproduction." The 

 latter, or germ-plasm, he assumes to possess an unlimited power 

 of continuance, and that life is endowed with a fixed duration, 

 not because it is contrary to its nature to be unlimited, but because 

 the unlimited existence of individuals would be a luxury without 

 any corresponding advantage. 



Herbert Spencer remarks upon this : — " The changes of every 

 aggregate, no matter of what kind, inevitably end in a state of 

 equilibrium. Suns and planets die, as well as organisms." But 

 has the theory been proved, either by the histologist, the micro- 

 scopist, or the chemist ? Spencer presses the point that the 

 immortality of the protozoa has not been proved. And, after all, 

 when Weismann makes the continuity of the germ-plasm the 

 foundation of a theory of heredity, he is building upon a pure 

 hypothesis. 



From the continuity of the germ -plasm, and its relative 

 segregation from the body at large, save with respect to nutrition, 



