APPENDIX D. xcix 



One of the best examples of this mode of 

 reproduction is met with in Colpoda cu- 

 cullus, which seems to divide only when in 

 the encysted state. As a general rule, the 

 process of fission only occurs once, but 

 it may be repeated, so that four, eight, 

 and even sixteen segments are produced. 

 There is also the further peculiarity, that 

 such segments generally encyst themselves 

 while still within the parent cyst. 

 Stein also speaks of the development of em- 

 bryos in certain -Acinetce, after an excep- 

 tional method : the substance of the 

 encysted animal appeared to give rise, 

 by a process of division, to six or more 

 embryos 1 . 



b. Resolution of the jm'0-segments into ' brood 

 cells/ containing a multitude of monadi- 

 form ciliated germs 2 . 



This process has been observed by Stein in 



Vorticella microstoma and V. nebulifera, 



and by Cienkowski in Nassula viridis. 



The differences between the cases ranged under A and 



B respectively are rendered much less absolute by 



the fact that Vorticellina undergo the process of 



fission when they are only one step advanced towards 



encystment that is to say, after they have withdrawn 



their ciliary apparatus and contracted their body 



into a more or less rounded or oval state, though 



previously to the production of a cyst. 



1 Pritchard's ' Infusoria,' 4th ed , p. 364. This is the process referred 

 to at p. xcvii. 



2 See Pritchard's 'Infusoria/ pp. 357, 258. There are good reasons 

 for believing that some of these tubulating ' brood-cells,' so produced, 

 develop into fungi belonging to the genus Pbyihium. 



8* 



