228 



BIOLOCY OF THE PROTOZOA 



B. Endogenous Budding. — This type of unequal division is not 

 so widely distributed amongst Protozoa as is exogenous budding 

 and is apparently not represented at all in flagellated forms. It 

 does occur, however, in all of the other groups. 



In Sarcodina endogenous budding has been described mainly in 

 connection with the testate rhizopods. In Centropyxis aeuhata 

 according to Schaudinn (1903) it leads to gamete formation, but 

 in Arcella vulgaris', according to Swarczewski (1908) and Elpatiewsky 

 (1909) it is a form of asexual reproduction. 



In Infusoria internal budding is characteristic of many types of 

 Suctoria, but is apparently not represented in the Ciliata. In the 

 simplest cases the budding area at the anterior end becomes internal 

 by insinking of the anterior surface and constriction of the body 

 walls on all sides, so that the reproducing area is enclosed by living 



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Fig. 117. — Endogenous budding in Suctoria. A, B, two stages in the formation 

 of a bud (b) and (c), of Tokophrya quadri partita; C, Acincta tuberosa with endogenous 

 buds (e) and (d). (From Calkins after Butschli.) 



protoplasm which thus becomes a potential brood chamber within 

 which the buds develop. Such buds may be single, as in Toko'phrya 

 quadripartita (Fig. 117, A, B), or multiple as in Metacineta (Fig. 

 117, C), and are always provided with cilia either as girdles or 

 otherwise. Through the activity of these cilia the buds swim freely 

 about in the brood chamber until they finally emerge through a 

 "birth-pore" and after a variable period as free swarmers or as 

 parasites in other Infusoria, they develop into adult forms of 

 Suctoria. Cilia in Suctoria are thus confined to the embryonic 

 stages and their various arrangements on the buds of different species 

 recall the types of ciliation in the other branch of the Infusoria. 

 A biologically interesting phenomenon of internal budding is 

 described by Collin (1911) in the case of Tokophrya qjchpum. Here 

 a brood pouch is formed by the cortical protoplasm within which 



