24 



INVEETEBEATA 



CHAP. 



produced, and those variations are preserved which adapt the 

 organism at the right time to the new mode of hfe. 



A 



Fig. 9. — The stalked larva and adult form of A ntedon muUispina. (After P. H. Carpenter.) 



A, larva. B, adult. &, Basal plate ; cir, cirrus ; pin, pinnule ; r^, first radial plate ; 

 7-3, second radial plate ; r'^, third radial plate. 



If J then, the last stages in developmental history are, so to speah, 



