SECT. m. PR AY A DIPHYS. 105 



and the digesting apparatus lies in the centre. Each 

 polypite is supplied with food by its own fishing-line 

 descending from a point close to where the polypite is 

 fixed to the long axis. It is a long, tubular, branched 

 tentacle, each branch ending in a coloured, pear-shaped, 

 or fusiform battery of thread-cells with their stings. 

 A gelatinous plate is placed on the upper side of the 

 common axis immediately over the isolated groups, to 

 protect and separate them. 



Such are some of the most general characters of the 

 family Diphyidse : the Praya diphys has something pe- 

 culiar to itself. 



In the Praya, each individual group has a swimming- 

 bell of its own adjacent to the polypite, and lying paral- 

 lel to the axis of the animal, with its mouth turned 

 backwards. It is connected by tubes both with the 

 general central canal, and with a helmet-shaped protect- 

 ing plate. On the other side of the polypite, there is a 

 tuft of vermiform buds with spiral terminations, bristled 

 with thread-cells. From the centre of this tuft a ten- 

 tacle, or fishing-line, descends with numerous branches, 

 the whole forming a tubular system connected with the 

 common canal in the axis. Each of the branches of the 

 tentacle terminates in a vermilion-coloured tendril, 

 coiled up into a minute capsule. The inside of the 

 tendril is not only bristled with the points of sabre- 

 shaped darts, but it conceals a filament crowded with 

 thread-cells. On the slightest touch, the tendril 

 stretches out like a corkscrew of red coral, and every 

 dart springs forth. Such is, more or less, the compli- 

 cated structure of the offensive and defensive weapons of 

 many of this order of oceanic Hydrozoa, which appear 

 to the naked eye as merely brightly-coloured points. 

 The use of these tentacles, or fishing-lines, is the same 

 in all ; they seize, kill, and carry their victims to the 

 mouth of the polypite by contracting their long lines. 



