PHYSOPHORIDE. ' 139 
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 ate 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 
