6 



GENERAL EMBRYOLOGY 



redifferentiation. After multiple fission or speculation, 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 ''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., Ephelota 

 (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 nr if prfl Prplpntprflt* PlfltvhplTYiiTV 

 After Wallengren. Division rc era > ^ Q eraia, natyn< 



stage immediately before the thes, Annulata, Bryozoa, and Tuni- 



separation of the daughter cells. .. . _ x T , , ,. 



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 



