80 



BRANCH VERTEBRATA. 



cartilaginous rod, above which is situate the nervous 

 system, while below is the alimentary tract. This animal 

 is found along the sea-shore buried in the mud. 



FIG. 148. 



CLASS TUNICATA (tu m ka'ta). 



The TUNIC ATES (tu'mk atz), also found along the coast, 

 are quite different in their adult structure. They occur 



either as single individuals of 

 the size of an acorn ; or they 

 may be smaller, almost micro- 

 scopic, and, united in colonies, 

 cover submerged rocks and sea- 

 weeds as a gelatinous mass. 

 But it is the young, or larval 

 Tunicata, that demands our 

 attention. This, as will be ob- 



Tadpolo-like larva of Tunicata attached -, -, -, . 



by the anterior portion of its body, and served by reference to the dia- 



adult degenerate form. The arrows in- crrftrrt "hnc; a nnnnrtino- n TQPO- 



dicate the course taken by watrr and g r < n > Iia 



food as they enter the mouth and leave me nted Cartilaginous rod, the 

 the Bpiuacular opening. E, Eye. 



so-called notochord (no' to kord), 



over which extends the nervous system, and below which 

 is the alimentary tract, a general structure, resembling 

 that of the young frog. After this stage, however, the 

 Tunicate becomes sedentary, retrogrades, and finally loses 

 all vertebrate peculiarities. All the remaining animals 

 may be spoken of as Vertebrates proper. 



CLASS ACBANIA (a kra'ni a). 



The little AMPHIOXUS (am n ox' us), or LANCELET (lans'iet), 

 has long been regarded as a vertebrate animal. It is small 

 and lanceolate in form, seldom exceeding two inches in 

 length. It is generally found buried in the sand of the 



