HYDRODICTYON UTRICULATUM 441 



Hydrodictyon utriculatum, Roth 



Observations may with advantage be made on Hydrodictyon^ 

 because of the very peculiar formation of the tissue composing its 

 network. It is not, however, of very frequent occurrence : and it 

 is to be found floating as a hollow sac-like net in still, fresh water 

 in summer. Observation with the naked eye will show obviously 

 the meshes of the net-work. 



Mount a small piece in water and examine under a low power : 

 the four- to six- angled meshes will be seen to be limited by as 

 many cells, which are of large size. Each cell contains numerous 

 nuclei, as may be ascertained by suitable staining. When a new 

 network is to be formed, the protoplasm of one of these cells 

 divides simultaneously into 7,000 to 20,000 parts ; these move 

 about within the original cell-wall, and finally arrange them- 

 selves in a new net-work, which, on growing, is liberated by 

 rupture of the parent cell- wall. This process may be observed in 

 healthy specimens in the height of summer. 



The whole cycle of life is a complicated one, and is somewhat 

 difficult of observation : as the organism is a rare one the various 

 stages will not be described at length. 



