1883. ] Zoölogy. 979 
The young forms, just set free from their parents, have a re- 
markable power of movement in the ectoderm ; this periodically 
thickens into tubercles which are best developed in two circular 
regions, but the number of tubercles is not constant. They may 
to less favorable conditions of existence. 
eview and comparative account of the Hydroidæ leads to 
the belief that in Hydra we have to do with a form which has 
been partly degraded and certainly modified. in adaptation to its 
fresh-water habitat.—/ourn. R. Micr. Soc. 
Kunstter on THE FLaGELLata.—In the Bull. Soc. Zool. de 
France for 1882, J. Kunstler contributes some facts to our know- 
ledge of the Flagellata. Heteromitus olivaceus, when treated with 
