20 GEORGE T. HARGITT 



cells show a more embryonic appearance after they have begun 

 to form the bud than they did before; especially is this true of 

 the entoderm. Nekrassoff concludes: ''on the ground of the 

 observations on the budding of Eleutheria we may conclude that 

 in the Coelenterates already differentiated cells have been given 

 the possibility of a reversible process — the possibility of taking 

 on anew an embryonic character." Regarding, the suggestion 

 of the origin of buds from germ cells, he finds in Eleutheria no 

 relation at all between sex cells and buds. 



The process of budding in medusae does not, as a rule, involve 

 any difference in principle from budding in Hydra and hydroids, 

 since both germ layers, by cell multiplication and evagination, 

 form the outgrowths which, by later differentiation, become the 

 tissues of the new individual. There are some buds which arise 

 from a small group of cells of a single layer, but in no case do buds 

 come from a single cell. Budding is not, therefore, a germinal 

 phenomenon, even when the new growth is derived from the 

 tissues of the gonads. Consequently, not only is there no neces- 

 sity for thinking of the germ plasm as being essential to the for- 

 mation of buds, but there is no evidence of the presence of germ 

 plasm in these buds. The conclusion of Nekrassoff, that differ- 

 entiated cells may take on again an embryonic character, seems 

 to explain the facts better than the germ plasm theory. Though 

 quite unaware of this conclusion of Nekrassoff, the author ('17) 

 worked out the budding of Hybocodon medusae and noted the 

 embryonic character of the cells involved in the budding process. 



There is considerable variation in the degree to which this 

 'reversible process' is exhibited by the tissues of medusae, but 

 an unbroken series may be arranged which includes all the known 

 types of budding. At one end of the series we may place the 

 medusae whose tissues do not have such a capacity; these repro- 

 duce only from fertilized egg cells. Here are included the 

 majority of medusae. If we accept the conclusions of Braem, 

 we may next place forms, like Lizzia and Rathkea, in which a 

 group of unfertilized oocytes may develop into a new organism. 

 This is a very unusual method and is applicable, so far as known, 

 only to the two forms named. Here the tissues either have no 



