LOBSTER. 73 



4. The abdominal ganglia : six pairs likewise 



connected by longitudinal commissures. 

 Diagram of the nervous system ! 



C. EXOSKELETON AND APPENDAGES IN DETAIL. 



I. Typical Abdominal Segment. 



Make, a diagram, of the third abdominal segment as 

 it ivould appear if seen in anterior or posterior 

 view, to show the form of the segment and its 

 appendages. 



II. Appendages. 



Take off all the appendages from one side of 



the body, beginning at the posterior end, being 



especially careful to remove each appendage entire. 



Observe : 



The appendages that bear the gills. 



The gills that are borne elsewhere. 



Compare each different kind of appendage 

 with the second maxilliped, and by refer- 

 ence to the chart * determine the homolo- 

 gous parts in the series. 



Find the scaphognathite. Of what parts is it 

 made up ? In what way can it move ? 



Of what parts is the telson composed ? 



Diagrams of : 



The third abdominal appendage. 



* Enlarged from Plate VIII, The Appendages of the Crayfish, 

 in "The Atlas of Practical and Experimental Biology," G. B. 

 Howes. 



