ORGANIC FORM AND ARCHITECTURE 



673 



of an animal is effected (a) by the nervous system which makes part 

 thrill to part ; {b) by the common fluid medium of the body (usually 

 the blood and the lymph) from which all parts take and to which all 

 parts give; (c) by the special "humoral" function of the blood, in 

 distributing the chemical messengers or "hormones" which play a 

 very important role in regulating the various bodily functions. But 

 we wish to point out here that the architecture of the body often 

 plays a humble, yet important, part in integration. The possession 

 of an axis, such as the backbone, implies some unification of bodily 

 movements. Similarly among backboneless animals the presence of 

 an exoskeleton — such as the cephalothorax shield of a crab, in which 



Fig. 93. 



A Peculiar Type of Alcyonarian Coral, Studeriotes, in which polyp-bearing 

 branches can be entirely retracted within a protective densely spiculose 

 cup seen in section in I. In another species (II) the cup-portion is not so 

 much expanded, yet the polyp-bearing branches are entirely retractile 

 (III) into the upper portion of the stalk. From specimens. 



many different muscles find insertion — secures the same consolida- 

 tion. So with the test of a sea-urchin, or the shell of a snail, or the 

 chain armour of a Bony Pike, or the carapace and plastron of a 

 tortoise, or the bony shields and rings of an armadillo; they may 

 all be credited with great measure of skeletal integration. 



It will be understood, then, that the two standards in reference 

 to which we decide the relative levels of organisation reached by 

 different animals (or plants) are differentiation and integration. 



CORRELATION OF ORGANS.~It is of the very nature of an 

 organism to be one; many members but one body. The various 

 organs are all partners in the business of life, and if one member 

 changes, others may also change. This correlation of organs is 



VOL. I XX 



