The Org/mism and its Major Parts 43 



The working out of these innumerable transformational 

 stages constitutes the science of embryogenetics. 



This transformational character of individual develop- 

 ment, or ontogenesis, is even more startling, and in some 

 ways confusing, in certain of the lower animals like the 

 coral polyps, where secondary individuals are produced 

 asexually but do not become wholly severed from the stock 

 or colony. But each multiple animal, as these may be called, 

 is a single germ-cell in the earliest stage of its life, and this 

 alone is proof of a certain measure of individuality of the 

 whole "colony" produced from the same Ggg. Indeed, some 

 zoologists, Huxley for instance ^ have used this as the sole 

 or chief criterion of organic individuality, and have defined 

 the individual as all that arises from a single germ-cell. 

 There can be no doubt about the validity and usefulness of 

 this conception as one criterion of individuality, even though 

 it does not constitute a basis for a complete definition. An 

 exceedingly fertile field of zoological research is that of the 

 varying degrees and exact character of functional as well 

 as developmental integration in these metagenetically built- 

 up, loose animal individualities. Much is already known 

 on the subject, but very much is not known, and to extend 

 knowledge in this field is one of the urgent needs of zoology. 

 The subject received much more attention, relatively, two 

 or three decades ago than it does now; so that few of the 

 investigations on which he have to rely have had the benefit 

 of the best technical methods. We may confidently antici- 

 pate that when the later technique of studies on neuro-mus- 

 cular stimulus and response and on internal secretions are 

 applied to metagenetic group-individuals, such as are found 

 in many of the coelenterates and in some of the tunicates, 

 much new light will be thrown on the interrelationship of 

 the members and organs in these poorly unified individuals. 



But — and the point is cardinal for us — no matter how 

 much or what new knowledge we get as to the members and 



