346 SYNOPTIC COLLECTION. 



(second and first pairs). In front of these walking-legs 

 there are a pair of arms which in the embryo cannot be 

 distinguished from the other walking-legs, but which in 

 course of development twist and stretch out forward, 

 becoming arms for catching food and for anchoring. 



Sometimes these organs through injury, by accident, 

 or through other unfavorable conditions, become de- 

 formed and often in such cases the specimens show the 

 strong hereditary tendency possessed by the claw to pro- 

 duce its like. In the thirty-five specimens of deformed 

 lobsters' claws in the collection of the Boston Society of 

 Natural History there are five which have developed an 

 additional claw with a movable jaw. This jaw is fastened 

 invariably either to the immovable jaw of the lobster's 

 claw or to the section from which the latter grows. In no 

 case does the movable jaw make a mock claw with the 

 true articulated jaw. 



In front of the arms are the three pairs of maxillipeds 

 and one pair of maxillae which are used in obtaining 

 food and carrying it to the mouth. These nine pairs of 

 appendages belong to the thoracic region. The seg- 

 ments to which they are attached are immovably con- 

 solidated, as we have said, and their dorsal portions have 

 disappeared, owing probably to the fact that the dorsal 

 and lateral portions of the fifth segment have grown out 

 backward in the form of a carapace, thereby covering 

 them and making their dorsal portions unnecessary. 



In front of the maxillae is another pair of leaf-like 

 maxillae and in front of these a pair of hard mandibles. 

 The mouth parts maxillipeds, maxillae, and mandibles 

 are placed snugly together, when at rest, but when the 

 animal is eating they are all in active motion. 



In front of the mouth parts are the two pairs of 

 antennae, one long and one short, and the pair of mov- 

 able eye-stalks with the compound eyes at their ends. 

 The last rive pairs of appendages described belong to the 

 cephalic region and their segments are consolidated like 



