PHYSOPHORfD^E. 



in the internal cavity of the stem of the polyp. Each fragment of 

 the line is capable of a prodigious extent of elongation and contrac- 

 tion : but where completely drawn back the pieces fold themselves up 

 somewhat in the manner of a pocket foot-rule. It is to the combined 

 effect of contraction and the unfolding of the pieces that these lines 

 owe the marvellous changes of length which they present." In 



Fig. 47. P. hydrostatica, with a portion of the disc, three polyps, and reproductive clusters 



attached. 



Fig. 47 are represented the polyps and fishing-lines of P. hydrostatica, 

 with a portion of the disc and two pairs of reproductive clusters. 



In this figure it will be observed that each fragment or joint has 

 implanted, near the articulation, a secondary line, which bears the 

 stinging organ. Each of these filaments consists of three parts a 

 straight stem, muscular, contractile, and hollow, the cavity of which 

 communicates with that of the trunk which carries it ; a middle part, 

 a sort of tube containing, in a considerable internal cavity, a trans- 

 parent liquid ; finally, an inflated stinging organ, which terminates 

 the apparatus. This last is egg-shaped, and consists internally of a 

 hyaline substance of cartilaginous consistence, in the interior of which 



