ORIGINS OF AGAMIC PATTERNS 633 



tute the basis of spatial pattern of organisms. They are either patterns 

 of dead products of metabolism or reactions of protoplasmic molecules 

 to limiting surfaces, mechanical factors, and probably other factors. They 

 may be definitely oriented with respect to an organismic pattern already 

 present or a reaction to purely local conditions. 



SYMMETRY IN CERTAIN MULTICELLULAR BUD PATTERNS 



The terms "bud" and "budding" have often been used loosely by biolo- 

 gists to include forms of development representing fission rather than 

 budding. As regards axiate organisms, budding may perhaps be defined 

 and distinguished from fission as a localized activation in an organism, 

 resulting in development of a new polar pattern of individual, organ sys- 

 tem, or organ. In fissions of axiate forms the polar pattern is not an en- 

 tirely new pattern but a reconstitution in relation to a part of the parental 

 pattern. Buds apparently represent the beginnings of polar pattern. In 

 other types of axiate agamic development and in embryonic development 

 pattern is already present when development begins. In certain types of 

 agamic development, usually called "budding" — for example, intercalary 

 development of zooids in many annelids and the so-called "stolons" in cer- 

 tain Syllidae — the "bud" continues posteriorly the axiate pattern of the 

 parent. In origin it is essentially similar to a reconstitution, but it is 

 more or less physiologically isolated and may become a sexual individual, 

 differing in form from the asexual parent. Whether we regard these zooids 

 as products of budding or fission is perhaps a matter of opinion, for in 

 origin they show resemblances to both. 



The only pattern at present distinguishable in early stages of the sim- 

 plest bud forms is a radial gradient pattern, representing the radial de- 

 crease of activation from a central region of primary or most intense ac- 

 tivation. In consequence of differential growth, or probably in some 

 cases differential cell migration, the radial gradient system becomes a 

 longitudinal axial system (pp. 16-21). There is no evidence that any 

 other pattern than this gradient system and its changes is necessary for 

 axiate development and differentiation from a bud. However, even 

 though the bud represents a new axiate pattern, certain features of its 

 pattern may be related to, and determined by, the pattern of the parent 

 individual. Lateral buds of many multiaxiate plants — for example, many 

 conifers — give rise to branches dorsiventral and bilateral in pattern in 

 consequence of their relation to the main axis. If the growing tips distal 

 to such a branch are removed, it becomes erect and radial in its further 



