2 7 6 



ELEMENTARY ZOOLOGY. 



tioned above, and for this reason are especially interesting 

 to the biologist, although they are not important animals 

 in nature. These include the worm-like Balanoglossus, 

 and the Tunicates or sea-squirts. Examine figures and 

 descriptions of these in the texts and answer the following 

 questions with respect to them : 



FIG. 107. Lake Lamprey (Petromyzon), clinging to sucker. From U. S. Fish 

 Commission, by Surface. 



Questions on the Figure. What are the evidences that the Lam- 

 prey belongs to the Chordata? How would you describe the mode 

 of life pictured here? Is it parasitism or simple preying? What 

 mouth structure has the lamprey that fits it for this life? What 

 references can you find to the breeding habits of lampreys? 



Where do they live? What is there about their struc- 

 ture that suggests that they are chordates? What seems 

 to relate them to invertebrates? What is the difference 

 between the larval and the adult condition in the sea- 

 squirts? Are there any tunicates that do not become 

 attached when adult? 



290. Some Lowly Chordates: a Library Exercise. 

 Here may be included the Amphioxus (lancelet) ; and the 

 Lampreys (Fig. 107). In what respects are these closer 



