1909] LEAVITT—HOMOEOSIS IN PLANTS 37 



often- and well-explored country a race of deviants undergoing a 



the species could 



from 



hardly have escaped observation. It is necessary 



structure 



this individual, supervened suddenly. The supernumerary spurs 



formed 



struc 





tures, except when regarded as sepallary appendages, and their 

 origin morphogenetically and historically considered is easily dis- 

 covered. The spur elaborated and perfected by the usual evolu- 

 tionary processes— whatever the "usual" processes may be— as an 

 appendage of the lip, has in a moment been transferred in full char- 

 acter to parts which heretofore have not been concerned— namely, to 

 the sepals. 



The principle is not new in biology. More than a century ago it 

 began to be observed that when a part of such an animal as a worm 



is cut off, 



a new part different from that removed, but like some 

 other part, may grow from the cut surface. 6 Boknet believed that 

 there are special germs for the development of the various organs; 

 as head-germs and tail-germs. From his experiments he made cer- 

 tain inductions concerning the distribution of these germs. Loeb 7 

 has investigated the conditions under which substitutions for lost 

 parts may be induced, this process being regarded by him as essen- 

 tia y different from regeneration and deserving the distinct name 

 eteromorphosis. Loeb also discovered that in some cases hetero- 



wn,md° S1S - Can . be produced with out any organ being cut off, or any 

 Wo »"d being inflicted upon the animal. Other investigators have 



to tb Wlth thC matter on ex P e rimental lines, especially with reference 

 e physiology of the process. Weismann has independently 



dealt 



argued 

 normal 



8 U1C1 » lw ^S 



ae. He uses the word hetero- 



the a m conne ction. 8 Bateson, who appears to have discovered 



nameTo 01 ^ 6 ^ *" ° riginal wav in his studv of variation, gave it the 

 6 Bo° m ° eOS1S ' 9 He descriDes cases in several phyla; for example, 



24 7- 1779. T ' CH "' ° euvres d ' his toire naturelle et de philosophic 1:191, 215; 3: 



7 Loe 

 The 



8 



B ' J ;' StUdies in 8 en «-al physiology 115, i 0I , 627. 1905. 



Thompson) 



\r... ,. ' \"«**«>i. uy XtlUMPSON) 



•^tenals for the study of variation 85^894. 



