138 _ A. OKA. 



4. Budding. 



Tliis mode of reproduction in Polyzoa has been studied by numer- 

 ous investigators, but their opinions ure more or less divided, especially 

 us to the origin from which the bud receiv^es its h^^poblastic elements, 

 and consequently, with regnrd to the relations of the germinal layers. 

 Most of them derive tlie hy[)oblast from the outer layer of the 

 enclocyst, while a few are inclined to believe that the bud receives it 

 from the gastric organ of the mother polypide. 



According to Allman (1), who describes the process of budding 

 in Lop]iopm and Alcijonella, the outer la3'er of the end(jcyst gives rise to 

 all the lining cells of the alimentary canal, while the lining epithelium 

 of the mother polypide becomes also the lining epithelium of the Ijud. 



Metschnikoif (7) gives an account of Ijudding in the embryo of 

 Alcijonella. He found that after continued segmentation of the egg, 

 the cells arrange themselves into a two layered hollow sphere, both 

 layers of which enter into the constitution of the bud, the outer 

 giving rise to the outer layer of the tentacles, the inner lining of the 

 alimentary canal and probably also to the nervous ganglion, and the 

 inner, to the lining epithelium and all the muscles. 



Nitsche (<S) studied the process of gemmation in AlctjoneUa 

 fimgom and Cristatella mucedo. In both species, the wall of the 

 alimeiittu-y canal is formed from a part of the endocystic invagination 

 of the mother polyzoiiid. In other words, the lining layer of the 

 alimentary canal is deri\ed from the outer layer of the body-wall. 

 Both Metschnikoif and Nitsche regard the outer layer of the endocyst 

 as the ectoderm and the inner as the entoderm. 



Hatschek's (4) acccjunt of l)udding in Cristatella is as follows. 

 A hollow sac lies directly beneath tlie outer layer, invested by 



