LOBSTER OE CEATFISH 155 



portion. Does the tendinous portion branch? If 

 so, to what is the branch attached ? To what 

 part of the mandible is it attached ? Pull on the 

 muscle and notice the movement of the mandible. 



e. The antennary and other muscles. — Examine 

 the basal joints of the antennae, antennules, and 

 ophthalmites, and note the small muscle strands 

 running from the joints to adjacent portions of 

 the exoskeleton. "With fine-pointed scissors split 

 these organs open lengthwise. Do the muscles 

 extend into these appendages ? 



/. The muscles of the great chela. — With a scal- 

 pel cut through the articular membrane at the 

 base of this appendage and remove it entire. 

 Notice that the muscles of the basal joints are 

 attached to ingrowths of the sternum, the endo- 

 sternites. With a pair of bone forceps cut 

 around the edges of the propodite and the dac- 

 tylopodite and remove the shell. Do the muscles 

 entirely fill these segments ? With a scalpel make 

 a vertical cut, about half the thickness of the 

 muscle, running from the angle between these 

 two segments to the outer corner of the base of 

 the propodite, and remove the inner half of the 

 muscle which is thus divided. JSTotice the cen- 

 tral tendon. How do the muscle fibres in the 

 propodite run with relation to this tendon ? Ee- 

 move the remainder of the muscle mass, thus ex- 

 posing the entire upper surface of the tendon. 

 What is its shape ? Size ? With a pair of for- 

 ceps grasp the posterior border of the tendon 

 and pull upon it. To what is it connected at its 

 outer end ? What motion does it produce ? Can 



