COMB-BEARERS. 31 



/urn), is found off the coast of Spain, and noted, as are 

 all the Alcyonarians, for its luminous properties.* 



Class III. COMB-BEARERS (Ctenophord). 



These are jelly-like animals, having, as organs of loco- 

 motion, vertical rows of comb-like paddles, that move up 

 and down in exact measure as they 

 travel along, glistening with rain- 

 bow-like hues. So vast are their 

 numbers that in the North they 

 often color the sea. They are not 

 only iridescent but luminous, their 

 very eggs and embryos giving out 

 light. The Bolina, Beroe, Idyia, 

 Cestum, and Pleurobrachia (Fig. 

 29), are all common on our New 

 England shores. The eggs are de- 

 posited singly, as in Pleurobrachia, 

 or in strings, as in Bolina, in the 

 autumn or last of summer, the 

 young passing through no changes, 

 and resembling the parent as soon 

 as hatched. 



Specimens for Study. The Hy- 

 dra can be found in any pond during the summer months, 

 and the salt-water forms from old piles and rocks along 

 the shore. Jelly-fish can be preserved in alcohol by grad- 



* All the Alcyonarians dredged by the Challenger were wonder- 

 fully luminous, and the bottom of the sea is undoubtedly lighted to a 

 more or less degree in this way. Great patches of light have been 

 seen sixty feet below the surface, while the small forms in shoaler 

 water vie with those of the greater depths. Professor Moseley exam- 

 ined the light of three Alcyonarians with the spectroscope, and found 

 it to consist of red, yellow, and green rays only. A glass containing 

 numbers of the Veretilhtm has given out light sufficient to read by, 

 and was distinguishable for some distance. 



FIG. 29. Pleurobrachia. 



