BUDDING. 



45 



The development of the buds and the branching of the stock thereby 

 determined takes place in the different forms of Bryozoa according to definite 

 laws which were long since reduced to certain written formulae. For the laws 

 of growth of the colonies, which cannot here be entered upon in detail, we refer 

 the reader chiefly to Davenport's treatise (No. 11). Braem, for Plumatella, 

 has composed a formula which also applies to the other Phylactolaemata. 



B 2 



B l 



C 1 



J) E 



a 



In this, the parent and offspring are always connected by a bracket | | thus. 

 This formula will be explained by comparing it with Fig. 21. The primary 

 individual A has given rise by budding 

 to the individuals B, B\ B 2 ; B, on its 

 side, has produced C and C 1 , and so 

 on. The individuals A, B, C, D, i.e., 

 the so-called principal buds resulting 

 from the first division, serve for the 

 continuation of the principal stem in a 

 centrifugal direction, while the inter- 

 mediate buds B 1 , B' 2 , B s , etc., become 

 intercalated between the oldest bud and 

 the mother A, and lead to secondary 

 branching of the stem. The order of 

 succession in the two cases is reversed. 

 Of the principal buds, the distal indi- 

 vidual which denotes the tip of the 

 branch (in this case G) is the youngest, 

 while of the intermediate buds B 1 , B 2 , 

 B 3 , the last-formed individual (B 3 ) lies 

 nearest to the mother-individual A. 



The number of buds that each indi- 

 vidual is capable of producing is often 



limited. In Cristatella, for instance, only two buds are, as a rule, produced, 

 the elder being a lateral bud and the younger a median bud. In Paludicella, 

 on the contrary, each individual is able to produce a median bud and two lateral 

 buds, and so on. 



The variations in the appearance of the Bryozoan stocks are caused- by the 

 constitution of the zooecial wall, which through stronger chitinisation or 

 impregnation with lime salts may become stiffened, or, on the other hand, may 

 be soft (Cristatella) or even gelatinous (Alcyonidium, Flustrella), and by the 

 more or less close juxtaposition of the single branches. When the latter 

 retain their independence, moss-like colonies with serrated branches are formed. 

 When the separate branches lie so close to one another in the same plane that 

 the neighbouring branches fuse together, leaf-like, fan-shaped, or encrusting 

 colonies are produced, while close crowding of the branches in various planes 

 leads to the development of fungoid forms (Plumatella fungosa). The fusion 

 of the separate zooecia has gone furthest in Cristatella, in which the originally 

 distinct character of the branches is indicated only by the mesodermal septa 

 growing in from the edge of the colony. 



Fig. 21.— .4, branch of Plumatella fruticosa 

 (after Braem). B, diagram illustrating the 

 branching of this form. 



