REPRODUCTION 



169 



or end to end; but in one species, Sijllis ramosa (Fig. 67), lateral budding 

 is the rule. The groups of worms in which budding occurs are in general 

 the simpler ones. Among the higher segmented worms are species in which 

 budding is common, and in certain still higher groups budding is a frequent 

 method of reproduction. Even in the Chordata, usually regarded as 

 the most complex group of animals, some of the simpler members 

 (ascidians) reproduce in this way. Figure 126 shows a colony of ascid- 

 ians produced in this manner. Budding is also common among many 



'»^ /.^F- 



fia 



tent 



cloaca 



atrMp 



B 



Fig. 126. — The colonial ascidian Pyrosoma. A, external \'iew of the entire colony, 

 diagrammatic; B, longitudinal section of a colony, diagrammatic; atr. ap, atrial aperture; 

 CO; colonial apertuie; m, mouth of individual; or. ap, oral aperture of individual; ph, 

 pharynx; proc, process of test; stol, stolon from which buds arise; lent, tentacles; tp, test 

 process. (A from Metcalf and Hopkins, after Ritter; B after Herdman in Challenger Reports.) 



kinds of plants. Buds may or may not resemble the parents. Obelia, 

 Bougainvillea and the siphonophores furnish instances in which parent 

 and bud may be totally unlike. 



Internal Budding. — All of the examples of budding mentioned above 

 are in animals which produce their buds outside of the body, but bads 

 may be produced internally. Thus the freshwater sponges produce large 

 numbers of minute internal buds called gemnmles. A gemmule is a 

 small grovip of cells produced by proliferation of somatic cells within 



