6 



GENERAL EMBRYOLOGY 



redifferentiation. After multiple fission or sporulation, the 

 end products of the process are commonly minute and visibly 

 quite unlike the adult form; this they come to resemble only 

 through growth and differentiation, that is, through processes 

 of true development. 



A reproductive process closely 

 allied to fission is the familiar proc- 

 ess of budding. Here one or 

 several small outgrowths or u buds" 

 are produced from some portion of 

 the parent organism, and develop 

 into forms resembling the parent, 

 either before or after becoming de- 

 tached. This process frequently ap- 

 pears as a sort of unequal fission 

 and may indeed rightly be regarded 

 as such; but usually so great is the 

 disparity in size, as well as in extent 

 of differentiation, between parent 

 and buds, that the processes are prop- 

 erly distinguished. Budding occurs 

 in many Protozoa (e.g., EpJielota 

 (Fig. 6, A), some Rhizopoda), and 

 is quite frequent among the lower 

 Metazoa, particularly in colony form- 

 FIG. 5. Binary fission, in ing species. It occurs among the 



the Infusorian, Euplotes harpa. p nrl 'f pr o fVplpntprfltfl Plfltvhplmin- 

 After Wallengren. Division rc 6ra > ^ Q Grata, J aiyni 



thes, Annulata, Bryozoa, and Tuni- 

 cata (Fig. 6, B). In budding there 

 is ordinarily very little direct transference of structures, 

 the development of the bud occurring after it has been 

 completely delimited as a comparatively undifferentiated mass; 

 its development may then be almost complete before the 

 separation of the two organisms. Nor does this process involve 

 necessarily the loss of identity of the parent, which may con- 

 tinue to live and produce buds for a considerable period. 

 In a few Protozoa, fresh water sponges, Trematodes and 



Wallengren. 

 stage immediately before the 

 separation of the daughter cells. 



