262 ZOOLOGY 



Appendages of Cypris. 



1. 1st pair of antennae (antennules). 5. 2nd pair of maxillae. 



2. 2nd ,, „ 6. 1st „ thoracic limbs. 



3. Mandibles. 7. 2nd ,, ,, ,, 



4. 1st pair of maxillae. 



The antennae are usually adapted for walking or swim- 

 ming, and in some of the marine forms the shell is notched, so 



.iV||,j., Pig. 155. — Lateral view of Cypris can- 



If/ ■ dida. After Zenker. 



jB#^ ^^'-t "\ y- Antennules. 



1-..3«^j--r U; Ni 2. Antennae. 



/~^Ss y7 n^ ^ \ ^" Mandibles. 



( /"^K V'^fU/i/^ vA \ *■ ^^ maxillae. 



\//\iJ^^^^^^M''J''j — ^ 5. 2nd maxillae. 



that the antennae can be protruded even when the shell is 

 closed. In Cypridina the anterior pair bear olfactory hairs, 

 and in Cypris the second pair end in hooked bristles, by means 

 of which the animal can anchor itself 



The mandibles are strong and toothed ; they bear a palp, 

 which is usually elongated and leg-like. The second maxilla 

 functions sometimes as a maxilla, sometimes as a leg; there 

 are usually two, rarely three, thoracic legs ; the abdomen is 

 devoid of appendages, and is rudimentary ; it may end in a 

 caudal fork, as in Cypris, or in a plate beset with setae. 



The oesophagus expands into a crop, which lies in front of 

 the true stomach. The last-named region of the alimentary 

 canal gives off a hepatic diverticulum on each side, which is 

 prolonged into the cavity of the shell. The anus opens at the 

 base of the abdomen. These animals are entirely carnivorous. 

 A heart is often absent ; when it exists, as in Cypridina, it lies 

 on the dorsal surface, in the region where the body and shell 

 are in continuity. There are as a rule no special respiratory 

 organs, respiration probably taking place through the general 

 surface of the body. A shell gland is present, and opens in 

 the region of the second maxUla. 



There is a cerebral ganglion and a short ventral chain of 

 ganglia, which, however, often fuse together to form a com- 

 plex ventral nervous mass. The single eye of the Nauplius 



