The Comb Jellies and Others 8i 



animal recovers, and swims away apparently no worse 

 for the experience. 



This remarkable capacity of the tentacles, wherewith 

 the jellyfish is enabled to subdue its prey by stunning it, 

 is due to hundreds of minute stinging cells that invest 

 those organs. The cells are somewhat egg-shaped, 

 with thickened elastic walls, and each one contains a 

 coiled threadlike filament, one end of which is attached 

 to the cell. The free end is pointed (in the case of 

 some organisms it is barbed, in addition) and is charged 

 with a highly irritant poison (believed to be formic 

 acid). When organic matter, such as food animals or 

 other edible material — for the jellyfish eats both the 

 living and the dead — comes into contact with the ten- 

 tacles, the cells in the immediate vicinity of the col- 

 lision become excited and burst with such force that the 

 poisonous filaments are driven into the object. It is 

 to the noxious property of these myriads of poisonous 

 darts that the paralyzing shock is due. 



As I have already implied, the sexes are separate In 

 the jellyfishes. The spawning season of Aurelia and 

 Cyanea, which takes place in midsummer, Is often 

 marked by inordinately thick shoals of the congregating 

 males and females. The eggs are carried in the ma- 

 ternal pouches until they have developed Into little 

 pear-shaped bodies (planula) covered with short cilia 

 enabling them to swim. When they are liberated they 

 wander around for a short time, but finally find their 

 way to the bottom where they^ attach themselves to 

 plants and stones. Then begins a series of marvelous 

 changes in the growth and development of the jellyfish. 



In attaching itself, the embryo does so on the narrow 



