168 



SEA-SHORE LIFE 



The minute animal and vegetable organisms that are drawn 

 in with the water do not pass through the gill slits, but are caught 

 in the slime that lines the throat and passed around, entangled in a 

 cord of slime, into the stomach. 



The heart is a spindle-shaped tube lying under and near the 

 stomach. Curiously enougli it pimips blood in one direction for a 

 few moments, then rests, and piimps in the opposite direction. 



The Ijlood corpuscles are 

 mainly colorless and con- 

 stantly change their shape re- 

 sembling amoebce. Some of 

 the blood corpuscles are, how- 

 ever, of definite shape and are 

 often deeply colored, being 

 reddish, indigo, brown or 

 even Avhite. It has been f oun d 

 that when bacteria or other 

 disease germs are introduced 

 into the blood system, the 

 colorless blood corpuscles 

 seize upon them, and attempt 

 to engulf them. Sometimes, 

 however, they do not succeed 

 but are themselves destroyed 

 in the attempt to digest the 

 bacteria, and then the disease 

 conquers in the strife. 



The genital organs are 

 found close to the side of a 

 loop of the intestine, and their 

 duct opens at the dorsal spout. In common with many sedentary 

 and degenerate animals all tunicates are hermaphrodites, but the 

 same individual does not usually fertilize its own eggs. 



The "brain" or principal ganglion of the Tunicate is situated 

 midway between the two spouts, and is simply the remnant of the 

 larval brain. It is, however, of so little importance that if it be 

 cut out the creature lives quite well, and is even capable of contract- 

 ing in a normal manner when touched. The "brainless" animal 



Fig. !iS; CIOXA INTESTIXALIS. From 

 Woods Holl, Mass. 



