ENSIS, CUMINGIA 141 



The cerebral ganglia are plainly visible without further 

 cutting. They lie just posterior to the anterior adductor 

 muscle and in front of the mouth, and are widely separated. 

 They are connected by a narrow commissure, and each gives 

 rise to a cerebrovisceral and a cerebropedal connective and 

 to a number of nerves. The nerves that supply the anterior 

 part of the mantle and the anterior adductor muscles are 

 especially easily seen. 



5. If the specimen is one that is nearly or quite dead, it 

 is easy to dissect out the cerebropedal connectives and the 

 pedal ganglia, which are not far from the base of the foot 

 and not deeply embedded. 



6. Allow the foot to return to its normal position and cut 

 along the line of union of the inner gills. Without further 

 cutting the visceral ganglia may be studied. Their connec- 

 tives may be followed easily as far forward as the palps. 

 The posterior pallial and the branchial nerves may also be 

 seen. 



A drawing of the nervous system should be made. 



Drew: The Habits and Movements of the Razor-shell Clam, Ensis 



directus. Biol. Bull., 12, 1907. 

 : The Physiology of the Nervous System of the Razor-shell Clam, 



Ensis directus. Jour. Exp. Zool., 5, 1908. 



CUMINGIA TELLINOIDES 



In separate bowls of sea water place several Cumingia 

 which have been kept in moist sand for a few hours. Watch 

 the shedding of eggs (pinkish) or sperm (whitish) which 

 ordinarily will require at least thirty minutes. Transfer 30 

 to 50 eggs to a Syracuse dish containing clean sea water. 

 Then fertilize them by adding not more than a very small 

 drop of sperm suspension. Observe the developing eggs from 

 time to time, noting when the following stages occur: (1) 

 Blastula. Is this ciliated? (2) Gastrula. (3) Trochophore 

 larva. (4) Veliger larva. 



