MOLGULA MANHATTENSIS. 177 



Certain organs are distinguishable through the tough tunic 

 which incloses the body. The endostyle in the mid-ventral line 

 of the pharynx or branchial basket will serve as a guide in orient- 

 ing the animal. Determine dorsal, ventral, anterior, right and 

 left aspects. 



Make a drawing of an expanded animal. 



4. The tunic or test can be removed by cutting through it 

 with scissors, taking care not to injure the mantle or body-wall. 

 Enlarge the opening made in the tunic and strip it from the body. 

 Where is the tunic most firmly attached? Examine a small 

 piece of the tunic microscopically. Are blood-vessels visible 

 in it? Does it contain any cells? 



5. For further study use both fresh and preserved material 

 from which the tunic has been removed. Identify as many 

 organs as possible through the mantle. In a living specimen 

 note the beating of the heart (the heart is on the right side) and 

 the frequent reversal of the direction of the pulsations. The 

 endostyle, longitudinal pharyngeal folds, intestine, gonads, gono- 

 ducts, renal organ, and subneural gland are also visible through 

 the mantle. 



6. Note the muscle bands of the mantle which serve to con- 

 tract the body and especially the siphons. Where are the mus- 

 cles best developed? Is there any definite arrangement of the 

 muscle-bands? 



7. Fix a large specimen by pins through the siphons, and 

 with scissors and fine forceps remove a large section of the man- 

 tle from the left side, injuring the underlying pharynx as little 

 as possible. The large space between the pharynx and the 

 mantle, laterally and dorsally, is the atrium, or peribranchial 

 chamber, which is formed as an ectodermal involution. Into 

 this atrial cavity open the intestine and the gonoducts, and also 

 the numerous stigmata of the pharynx. 



Alimentary Canal. Cut out a piece of the wall of the pharynx 

 from a very fresh specimen and examine in sea-water with a 

 microscope. 



1. Note the meshwork of blood-vessels, and the openings or 

 12 



