THE WHALEBONE WHALES, 
265 
whales each ^^blow" in a double stream, which is directed 
backward toward the tail. 
Whales are rarely over fifty feet long; the sperm-whale 
has been known to reach a little over twenty-three metres 
(76 feet) in length, but Professor Flower questions whether 
the sperm-whale frequently, if ever, when measured iii a 
straight line, exceeds a length of sixty feet. The largest 
F-G. 302.— Fiu- whale. From Liitken's Zoology. 
of all wliales, as of all existing animals, is the fin-back 
(Pig. 302) or rorqual {Balmnoptera boops), which some- 
times measures thirty-four metres iu length. The smallest 
Cetacea are the porpoises. 
In the whalebone whales, the teeth, present in the em- 
bryo, become reabsorbed into the gums before birth and 
Fig. 303. — Outline of the cachelot, showing how the blubber is removed : b, the 
situation of the " case;" c, the junk; d, the bunch of the neck; /i, the hump; 
i, the ridge ; the small ; /, the tail or flukes ; between the oblique dotted 
lines are the spiral strips or blanket pieces. 
are replaced by plates of whalebone, three hundred of which 
may be present on each side of the mouth. The inner 
edges of these plates have projecting fibres, forming a rude 
strainer; these whales feed on small pelagic jelly-fish, mol- 
lusks, and Crustacea, by taking in a mouthful of water, and 
then pressing the tongue against the roof of the mouth, 
expelling the water through the openings between the 
