GLOSSARY 215 



Mantle : the integumental fold in mollusks which secretes the shell ; mus- 

 sel, 90 ; oyster, 100 ; clam, 104 ; snail, 113 ; squid, 124 : the body-wall of 

 ascidians beneath the tunic, 136. 



Manubrium : the projection of a medusa's body which bears the mouth, 

 167, 173, 175. 



Maxilla: the paired mouth-parts immediately behind the mandibles in 

 arthropods ; grasshopper, 13 ; beetle, 14 ; wasp, 14 ; caterpillar, 20 ; 

 spider, 25 ; crayfish or lobster, 30 ; sow-bug, 47 ; amphipod, 49 ; cope- 

 pod, 54 ; Daphnia, 56. 



Maxillipeds : the anterior thoracic appendages which assist in mastication 

 in crustaceans ; crayfish or lobster, 30 ; sow-bug, 47 ; amphipod, 49 ; 

 Caprella, 50. 



Medusa : a medusoid which becomes a free-swimming jelly-fish, 163, 169, 

 175. 



Medusoid : the sexual generation of a hydromedusan, 163, 169. 



Megalopa : a larval stage of the crab, 51. 



Mentum : a division of the labium in insects, 13. 



Mesentery : a lamella which supports some one of the viscera ; Nereis, 64 ; 

 Bugula, 86 ; squid, 127 ; starfish, 145 ; sea urchin, 152 ; sea cucumber, 

 156 ; sea anemone, 179. 



Mesosternum : the ventral surface of the mesothorax in insects ; wasp, 3 ; 

 grasshopper, 10. 



Mesothorax : the second thoracic somite in insects ; wasp, 2 ; grass- 

 hopper, 10. 



Metamere : one of the serial, homologous body-segments, together with its 

 appendages, which form the body of an articulate animal. 



Metamorphosis : the quiescent period in the life of a holometabolic insect 

 during which it changes from a larva to an imago. 



Metasoma : the primitive segmented trunk of an articulate animal, 62, 68. 



Metasternum : the ventral surface of the metathorax in insects ; wasp, 3 ; 

 grasshopper, 10. 



Metastomium : the posterior portion of the prosoma of an annelid, 62, 6.9. 



Metathorax : the third thoracic somite in insects ; wasp, 2 ; grasshopper, 9. 



Metazoa : the division of the animal kingdom comprising the many-celled 

 animals, 191. 



Micronucleus : the smaller of the nuclear bodies in inf usorians ; Parame- 

 cium, 186 ; Vorticella, 190. 



Mother-of-pearl : the inner layer of the shell of mollusks ; mussel, 91 ; 

 clam, 105. 



Moult : to shed the cuticula or the outer portion of it. 



