42 



INTERNAL STRUCTURE OF THE ASCIDIA. 



folds, represented by dotted 

 lines, as supposed to be seen 

 through the membrane, g is 

 the termination of the intes- 

 tine in the cavity, laid open. 



The heart in these animals 

 is a simple elongated tube, re- 

 ceiving at one end the blood 

 from vessels of the aerating 

 sac, and at the other branch- 

 ing out into vessels for the 

 supply of the system. 



Such, then, are the fixed 

 inert ascidise, animals desti- 

 tute of locomotion, and in 

 which the principal sign of 

 life is displayed in the ab- 

 sorption and discharge of the internal structure of the Ascidia. 



fluid in which they live. Belonging to the tunicate 

 group, however, are a number of curious marine ani- 

 mals, not like the ascidise, but free and swimming about 

 in the ocean, the warmer latitudes of which are their 

 principal abode. One species, holuthuria ananas, 

 found in the South Seas, is prized by the natives 

 of the Molucca islands as an article of food. Some 



