140 A. OKA. 



of the colony so characteristic for each species. What Er?em de- 

 scribes for Cristatella on this point does not apply in all its details to 

 the present species. 



At the plnce where buds appear, there is no muscular layer, as 

 already observed by Nitsche, and the endocyst may here be repre- 

 sented as consisting- of only two layers, viz. the outer cell layer and 

 the inner lining epithelium. The latter, in direct contact with the 

 former, passively follows all the changes in form undergone l)y the 

 outer layer of the endocyst. So, it must be borne in mind, that 

 when in desci-il)ino- different stao^es of budding", the changes of the 

 outer layer (which is the inner layer of the bud as will be seen fur- 

 ther on) alone are mentioned, similar chang'es are repeated by the 

 lining epithelium (the outer layer of the bud). 



At first, some cells of the outer layer push their way inward in 

 the form of a solid knol) covered by the lining epithelium (fig. 57. Ph 

 XX). At a certain observed stage in which the knob consisted 

 of eighteen cells, many more were on their way of entering. 



A cavity ultimately appears in the centre of the knob (fig. 58, 

 PI. XX.) and the cells arrange themselves regularly around it in 

 epithelial order. The cavity soon comes to communicate with the 

 exterior by means of a cajial formed by the gradual retreat of cells at 

 that part (fig. 5Î), PI. XX.). The bud now represents a double- walled 

 sac whose inner and oiitei- layers are respectively eontinuations of the 

 outer and inner la3^ers of the endocyst. Thus it is plain, that tlie. 

 bud originates not by direct invagination of the two layers of the 

 endocyst, but by the formation of a closed sac which secondarily opens 

 outward. 



As the bud grows in size, it inclines dowji wards and its oral side 

 is connected to the crenœcial wall along its wh(^le length by a me- 

 seiitary-like membrane whi<'h is the continuati<^n of the lining epi- 



