1903] Report on some Medusae from Norway and Spitzbergen. 27 



covered with nematocysts. These tentacles Haeckel calls "feelers" 

 or "taciile tentacles", and they are similar to those which I have 

 found in Ptyehogastria polaris. 



Allman in his description of Ptt/chogastria polaris writes: — 

 „The marginal lobes of the umbrella are in the form of short trun- 

 cated cones, each carrying several papilliform and probably exten- 

 sile proeesses, and separated from its neighbour by a deep noten. 

 The condition of the specimen, whose transparency was lost by its 

 preservation in alcohol, rendered it impossible to determine anything 

 regarding the lithocysts, while my unwillingness to destroy a unique 

 specimen has rendered the determination of some other points of 

 structure not so complete as I could have wished. Each tentacle 

 corresponds to one of the notches which separate the marginal 

 lobes. The tentacles are manifestly very extensile, but are easily 

 detached and have mostly fallen from the specimen. They have 

 the cavity divided into chambers by dose septa and show a very 

 distinct longitudinal fibrillation of their walls." 



The medusa has eight radial canals which are described by 

 Haeckel as being narrow. What I believe that he really saw 

 were not the radial canals, but the bases of the mesenteries atta- 

 ched to the sub-umbrella, as seen through the ex-umbrella. When 

 I first examined the specimens I made this mistake and it was not 

 until I removed the thick opaque layer of muscles on the sub- 

 umbrella that I discovered the error and saw the true radial canals. 

 The radial canals are very broad and flat, with very thin walls, 

 and decrease in width as they approach the stomach. The ring 

 canal is also very broad. Between each two of the eight radial 

 canals there is also a centripetal canal, which runs from the ring 

 canal nearly to the base of the stomach. These eight centripetal 

 canals are like the radial canals in shape. They have nearly the 

 same width as the radial canals on leaving the ring canal and 

 gradually taper to a fine point. 



The general external appearance of the mouth, stomach, and 

 gonads, has been very well figured by Haeckel (Taf. III. fig. 2.). 

 The eight gonads extend across the inner half of the sub-umbrella, 

 and the mesenteries, like fine membranes, extend from the stomach 

 along the centre of each gonad to the margin of the umbrella, tims 

 dividing the sub-umbrella cavity into eight compartments. When 

 I first examined the specimen I considered the gonads from their 



