COMB-BEARERS. 31 
lum), is found off the coast of Spain, and noted, as are 
all the Alcyonarians, for its luminous properties.* 
Class III.—CoMB-BEARERS (Ctenophora). 
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, Beroé, 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. FIG. 29.—Pleurobrachia, 
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 Veretillum has given out light sufficient to read by, 
and was distinguishable for some distance. 
