544 DR. F. W. JONES ON GROWTH-FORMS [Jvme 18, 



more vigorous lateral zooids, so that there is a tendency towards 

 brancli-formation below the site of injury. 



This state of things, when put into terms of the life functions 

 of the colony, means that potentially almost any lateral bud 

 possesses the inherent vitality of the apical zooid, but it is only in 

 times of stress to the colony that this potential power becomes 

 actual. A stem of a Madrepore colony may shoot up straight for 

 the distance of a foot, and show nothing more worthy of the name 

 of a branch than the normal projections of domina,nt zooids 

 scattered irregularly over its surface ; but if sufficient damage be 

 done to it to destroy the apical zooid as well as a fair portion of 

 its entire length, then the remaining part will at once start 



Text-fis-. 161. 



Type of repair of Madrepores when the " dominant apical zooid " is entirely 

 destroyed. Process at the end of 100 dajs. 



budding with vigour. The best examples of this mode of repair 

 are seen in those cases in which a colony is attacked by filamentous 

 algse. The thin green thi'eads of this parasite enmesh the branches, 

 and penetrating into their substance, lead rapidly and certainly to 

 the death of the part attacked. Artificially produced injuries 

 also provide good examples of this mode of repair. The first 

 stage is noticed when, in contrast to the dead terminal portion, 

 the living part sw^ells out, its dominant zooids become more con- 

 spicuous, and their projections increase until they arrive at a 

 stage at which they themselves give off lateral buds. The number 

 of these enlarged lateral zooids may be very great, but not all of 

 them ever- attain the dignity of actual branch formation. 



