THE ORDER AMONG ANIMAL TYPES 



115 



CHORD ATA 



\ 



FIG. 63. TUNIC ATA - SEA SQUIRT 



NERVE CORD 



NOrOCHORD 



PHARYNGEAL SUTS 



INTESTINE MUSCLE SEGMENT 



MOUTH 



ATRIOPORE 



HEPATIC GLAND ATRIUM 



GONADS 



ANUS 



FIG. 64. CEPHALOCHORDA-AMPHIOXUS (^WITH BODY WALL 



REMOVED) 



FIG 62. ENTEROPNEUSTA- 



BALANOGLOSSUS 



Fig. 62. — A representative of the sub-phylum Enteropneusta, of the phylum 

 Chordata; Balanoglossus. The larval form of Balanoglossus much resembles the 

 larva of Echinodermata. A notochord is present in the adult. 



Fig. (iT,. — Representative of the sub-phylum Tunicata, a sea squirt. The larval 

 form is free swimming and shaped much like a small frog tadpole. After attaching 

 itself it becomes transformed into the adult form as represented in the figure. 

 The upper opening is the mouth; the lateral opening is known as the atriopore; 

 the contents of the intestine and the water taken in through the mouth are ex- 

 pelled through the atriopore. 



Fig. 64. — Amphioxus, representati\e of the sub-phylum Cephalochordata. Diagram. 

 Note the dorsal position of the main nerve cord and of the notochord. The seg- 

 mental character of the muscles, the presence of pharyngeal slits and of a hepatic 

 or liver gland should also be noted. 



