HOMARUS AMERICANUS MILNE-EDWARDS 137 



and five pairs of pereiopods. The first three pairs of pereiopods 

 end in a double claw or chela. The chelae of the first pair are 

 especially powerful. One of them, the cracker claw, is developed 

 more than the other which is called the toothed claw. 



2. Examine the ventral surface of the lobster and make a 

 full page drawing of it. Identify the sex by the position of 

 the genital openings and by the structure of the first pair of 

 abdominal appendages. In the male the openings of the vasa 

 deferentia are situated on the inner surface of the basal joint 

 or coxopodite of the fifth pereiopod, and the first pair of ab- 

 dominal appendages are modified as organs of copulation or 

 stylets. In the female the openings of the oviducts are situated 

 on the inner surface of the coxopodite of the third pair of pereio- 

 pods, the fifth sternal plate forms a seminal receptacle, and the 

 first pair of abdominal appendages is poorly developed and 

 more or less filiform. Besides the appendages mentioned in 

 the preceding paragraph, there are visible the abdominal ap- 

 pendages or pleopods. Of the somites only the sternites are 

 visible. The telson shows the anus. 



3. Take the specimen into your left hand and looking, so to 

 say, into the mouth of the animal, make a full-size drawing 

 showing the appendages surrounding it in their natural position. 

 The following parts are visible in this position: the first and 

 second pair of antenna, triangular epistome or upper lip, man- 

 dibles with mandibular palpi, endopodite of the second pair of 

 maxillipeds, endo- and exopodites of the third pair of maxillipeds. 

 On the basal joint of the second pair of antennae the openings 

 of the green glands are visible. 



4. Remove the carapace by lifting it at the posterior edge and 

 cutting the muscles and tendons. The carapace will come off 

 with eyes and antennae attached to it. These should be re- 

 moved not by pulling but by cutting the joint-membrane with 

 sharp scissors. When the inside of the carapace has been cleaned 

 it will be noticed that the skeleton of the three preoral segments 

 remains firmly attached to the carapace. Holding the carapace 



