BUDDING IN HYDRA. 



GEO. W. TANNREUTHER. 



Budding in hydra has received the attention of only a few 

 investigators. Our principal information as to the origin of the 

 bud is derived from Lang's 1 account. He describes the bud as 

 beginning by an increase in volume and division of the interstitial 

 cells. After the ectoderm becomes thickened, the mesoglea dis- 

 appears and the cells pass from the ectoderm into the endoderm. 

 This process continues until the ectoderm becomes reduced to its 

 normal thickness. The mesoglea then reforms and a cavity ap- 

 pears in the thickened endoderm, which becomes the enteron of 

 the new individual. 



The main object of the present paper will be to give a brief 

 account of the origin and development of the buds in hydra, more 

 especially their manner of growth and what cells contribute most 

 to their rapid formation. 



The species studied, Hydra viridis and Hydra sp.? (Brauer) 

 differ somewhat from Lang's account. The mesoglea does not 

 disappear and the ectodermal cells do not pass into the endoderm. 

 The bud, however, begins by an increase in volume and division 

 of the interstitial cells. After they have increased once or twice 

 in volume, as shown in Fig. I, there is a slight outbulging of 

 the ectoderm, which is scarcely perceptible. Fig. 2 represents 

 the condition of the interstitial, ectodermal and endodermal cells 

 in the origin of the bud as they appear more highly magnified. 

 A few mitotic figures are visible. No amitotic divisions were 

 observed. The endodermal cells contain numerous food particles, 

 which may pass intact through the mesoglea into the ectoderm. 

 The cells directly concerned in the formation of the bud are well 

 supplied with food, while the remaining cells of the parent hydra 

 show a scarcity. Many of the endodermal cells in the distal half 

 of the hydra have a glandular appearance and are most active in 



1 Lang, Albert, " Uber die Knospung bei Hydra und einigen Hydropolypen," 

 Z. wiss. Zool., Vol. 54, 1892. 



2IO 



