ONTOGENY 7 



Bryozoa, internal buds are formed within the parent cell or 

 body (Fig. 7). These become free and develop into new indi- 

 viduals ordinarily only after the death of the parent body. 

 Although the formation of these gemmules (Porifera), or stato- 

 blasts (Bryozoa) suggests that form of reproduction character- 

 istic of the higher Metazoa, i.e., through internally forme'd germ 

 cells, it will appear later that the two processes are not at 

 all to be compared. 



FIG. 6. Reproduction by budding. A. In the Infusorian, Ephelota. From 

 Calkins, "Protozoa." N, branched macronucleus extending from the parent 

 cell into each bud. B. In the Tunicate, Doliolum. After Neumann. Ventral 

 outgrowth of a phorozooid. 6, reproductive buds of various ages; g, germinal 

 knob; s, stalk. 



In some of the shelled Rhizopods (Euglypha, Arcella) a 

 combination of the processes of budding and fission occurs. 

 In this process, called bud-fission, about one-half of the proto- 

 plasm flows outside the original shell, which these forms possess, 

 and secretes a new shell like that of the parent form; or the 

 rudiments of the new shell may be formed before the appear- 

 ance of the bud. The cell body then divides and the two similar 

 individuals may either separate completely, or they may 

 remain in contact, forming after repeated bud-fission, an 

 aggregate of related though distinct organisms. 



In many of the Protozoa multiple fission may be incomplete, 



