176 CHORDATA. 



collar to become turgid. In burrowing and feeding, of what 

 use to the animal is the collar? 



Note the characteristic coiling of the genital region in this 

 species. The anterior end, including the branchial region, is 

 normally maintained in a vertical position. The posterior 

 end is also kept upright, and can be moved up and down in a 

 vertical shaft opening on the surface, thus enabling the animal 

 to eject the residue of sand from the anus. 



For the internal anatomy, the account in the Cambridge 

 Natural History may be consulted. Important chordate 

 characters are the notochord, the dorsal central nervous system, 

 and the branchial arches. 



Agassiz: The History of Balanoglossus and Tornaria. Amer. Acad. Arts 



and Sci., 9, 1873. 

 Hitter and Davis: Studies on the Ecology, Morphology, and Speciology of 



the Young of Some Enteropneusta of Western North America. Univ. 



Calif. Pub. Zool, 1, 1904. 



MOLGULA MANHATTENSIS. 



Specimens of this simple ascidian may be found attached to 

 old piles, associated with many other forms. In some localities 

 they may be so abundant as to practically incrust the piles, and 

 crowd each other out of shape. Examine such a mass and see 

 how different sized individuals are associated. Pull them apart 

 and see if there is any tissue connection between them that 

 would indicate a definite relation between neighbors. Do you 

 understand how the individuals get started in the places where 

 they are attached ? With a glass-bottomed pail you can see the 

 expanded individuals on the piles, but they can be more satisfac- 

 torily studied in small dishes of sea-water. 



1. Observe the contraction and closure of the two siphons 

 when the animal is irritated. 



2. Add a little powdered carmine to the water to determine 

 which is the incurrent or oral and which the excurrent or atrial 

 siphon. 



3. Ascertain the number of lobes at the extremity of each 

 siphon. Are pigment-spots present on the siphonal lobes? 



