GENERAL BIOLOGY 



III. APERTURES. 



Make out the following apertures in the body wall : 



1. The mouth seen under the anterior part of the cephalothorax 

 after separating from one another the crowded appendages. 



2. Anus, a much elongated slit upon the lower side of the ter- 

 minal piece of the abdomen, the telson. 



3. Genital openings on the basal joints of the legs: (a) In the 

 male on the delicate papilla on the last appendage of the cephalo- 

 thorax (one on the right and one on the left) ; (b) in the female an 

 opening with a valve-like edge on the antepenultimate appendage 

 of the cephalothorax (one on the right and one on the left). 



4. Auditory organs : A small opening on the appendage (anten- 

 nule) just under each eye stalk. 



5. Green glands : A large opening on the ventral side of the 

 first joint of the next following appendage (antenna) on each 

 side. 



B. ABDOMEN. 



This is made up of six segments or somites bearing appendages 

 and a terminal, seventh piece, the telson, which is subdivided by a 

 transverse hinge and bears the anus. Carefully examine the third 

 abdominal somite. The following surfaces are found upon it: (a) 

 Tergum, the dorsal arched portion overlapped anteriorly by the 

 preceding tergum. (b) Sternum, the ventral portion between the 

 appendages, composed of a transverse bar and a more calcified 

 cuticle where movements take place in bending the abdomen, (c) 

 Pleuron, the downward projecting portion on each side, overlapped 

 in front by the pleuron of the preceding segment. The appendages 

 are attached to the body by soft flexible cuticular parts of the exo- 

 skeleton. 



Each abdominal appendage consists of the following parts : 



a. Protopo-dite : This is the proximal part of the appendage and 

 is divided into a long joint, and a small ring-like piece by which it 

 is attached. It bears distally two parts, 



b. Endopodite : This is the part nearer the middle line. 



c. Exopodite: The portion farther from the middle line. 



C. CEPHALOTHORAX. 



a. The large shield-like part of the exoskeleton covering the 

 cephalothorax above and on the sides is the carapace, which is pro- 

 longed in front into the frontal spine or rostrum. 



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