128 THE OCEANIC HYDROZOA, 



to have a proximal convex and a distal concave surface. They present many dots and specks, 

 which are for the most part aggregations of thread-cells. The hydrophyllia are capable of 

 independent motion, and in the undisturbed condition of the animal they are constantly 

 elevated and depressed. On irritating the creature they are all closely adducted, so as to 

 protect the organs over which they lie. The hydrocysts are from six to twelve lines long, 

 and almost cylindrical, and from the base of each springs a long tentacle. 



The polypites are six or seven lines long, even in the contracted condition. They have 

 six villous or hepatic ridges. 



The structure of the simple tentacles has been referred to above (p. 11). The gono- 

 phores have not yet been found attached to an entire hydrosoma, but Leuckart ('Z. N. K.,' 

 p. 71) describes them in the detached groups of appendages. 



They appear to be developed in bunches among the hydrocysts, and sometimes in con- 

 nexion with their peduncles, and the gynophores, at any rate, exhibit distinct calyces and 

 manubria ; the latter containing a single ovum. 



Leuckart observed a specimen of Jpolemia a foot long. Its pneumatophore measured 

 two lines, its nectocalyces from six to eight lines in length. 



