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THE BEGINNINGS OF LIFE. 



IL Reproduction by means of Gemmation, is a process 



which also slides by the most insensible gradations into 

 the process of fission. All intermediate grades may be 

 traced between the production of the most obvious bud- 

 like projection, and the process by which a single indi- 

 vidual is divided into two equal segments. In ordinary 

 fission the ' bud' is equal in size to the parent organism 

 (which is diminished to half its bulk), and each seg- 

 ment obtains half of the original ' nucleus/ In ordinary 

 gemmation, however, the new individual is produced 

 rather by a growth from, than by a division of, the 

 parent organism, and an entirely new ' nucleus ' is 

 evolved within the bud. The process of external gem- 

 mation, amongst the Ciliated Infusoria, is much rarer 



than that of fission. 

 The buds or gemmae behave very diff"erently according to 



the species under observation, and also, to a minor ex- 

 tent, even among individuals belonging to the same so- 



called 



species 



Some develop a posterior circlet of 

 cilia and swim about for a time ; they may then 

 (a) either develop a stalk or sheath and resume all the 

 characteristics of the parent-stock, or (-5), becoming 

 quiescent, they may encyst themselves preparatory to 

 further development. The young gemmae of Spirochona 

 diff'er from those of the Vorticellina generally, by the 

 non-developm.ent of the posterior ciliary wreath ; whilst a 

 development of cilia (lasting only for a time) takes place 

 anteriorly, before the gemma assumes the parent form. 

 In other buds of this species, however, according to Stein, 

 a process of encystment at first takes place, during which 

 the gemmae are converted into very peculiar Acinetiform 

 beings, usually known as Dendrocometes paradoxus. 

 The process of budding observed by Stein in Lagenophrys 

 presents many peculiarities, and, after alluding to his 



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