124 MOLLUSCA. 



3. Another ganglionic mass, the abdominal ganglion, possi- 

 bly formed by the fusion of two ganglia, lies just below the exter- 

 nal opening of the kidney, where it can be seen as a brown mass, 

 through the body-wall. It lies on the elongated commissure 

 that connects the two visceral ganglia. The commissure may be 

 followed by dissection. 



The cerebral ganglia are the most centralized. Besides being 

 connected with each other by a commissure dorsal to the esopha- 

 gus, and being intimately connected with the pleural ganglia, 

 each cerebral ganglion is connected with the corresponding buc- 

 cal and pedal ganglion, and, through the pleural, with the visceral 

 ganglion. The visceral ganglia are connected with each other 

 by a long commissure on which the abdominal ganglion is placed. 

 Each pedal ganglion receives connectives from the cerebral and 

 from the pleural ganglion of the corresponding side. 



Draw figures of the nervous system and compare them with 

 the clay model. 1 



Colton: How Fulgur and Sycotypus Eat Oysters, Mussels, and Clams. 

 Proc. Acad. Nat. Sci., Philadelphia, 1908. 



Conklin: The Embryology of Fulgur: A Study of the Influence of Yolk on 

 Development. Proc. Acad. Nat. Sci., Philadelphia, 1907. 



: The Embryology of Crepidula. Jour. Morph., 13, 1897. 



Glaser: tiber den Kannibalismus bei Fasciolaria tulipa (var. distans) und 

 deren larvale Excretionsorgane. Zeit. f. wiss. Zool., 80, 1905. 



Herrick : Mechanism of the Odontophoral Apparatus in Sycotypus canalicu- 

 latus. Am. Nat., 40, 1906. 



Orton: An Account of the Natural History of the Slipper-Limpet (Crepi- 

 dula fornicata). Jour. Marine Biol. Ass., 9, 1912. 



Patten: The Embryology of Patella. Arb. Zool. Inst. Wien., 6, 1886. 



CEPHALOPODA. 



LOLIGO PEALII. (The Squid.) 



Specimens of this or closely related species are rather common 

 along the Atlantic coast of the United States. They are active 

 swimmers, but may occasionally be seen in shallow, quiet water 

 near the shore. The movements and positions of adult speci- 



1 Instructors will find that a model prepared by sticking lumps and 

 strands of modeling clay on a cylindrical graduate, to illustrate the positions 

 of the ganglia and connectives on the esophagus, will greatly aid the 

 students. 



