384 INDEX-GLOSSARY. 



289; Nictitating, 229 ; m. semilunaris, 248; Shell m., 256; Subzonal, 



309; Tympanic, 219, 255, 273, 304; m. tympaniformis interna, 248; 



Vitelline, 73, 252, 299. 

 Mesenteron (/xeo-os, middle ; eWtpoz/, a bowel) That part of the alimentary 



tube which is lined by epithelium of hypoblastic origin ; the mid-gut, 48. 

 Mesentery (/xeVos ; 4Wpos, a bowel) (1) In Earthworm (.see Septum ; (2) in 



Vertebrates, a fold of peritoneum by which the alimentary canal is 



suspended, 161, 192. 

 Mesoblast (jue'cros ; /3\ao-Tos, properly anything grown; /W<rraj/w, I grow) 



The mesoderm of a developing embryo, 36. 

 Mesoblastic bands, 71. 

 Mesoblastic somites, 227, 263. 



Mesoblasts Cells in the embryo which gives rise to the mesoderm, 67. 

 Mesoderm (/xe'o-os ; oe'p/xct, the skin) The middle germinal layer and parts 



derived from it, 36, 68, 71, 106, 107, 149, 224, 226, 259, 263, 306, 308. 

 Mesoglrea, 20. 

 Mesonephros (/j.e<ros ; i></>po, a kidney), in Vertebrates The second-formed 



excretory organ, which, as in the Frog, may persist throughout life, 



166, 216, 265, 333, 334. 

 Mesopterygium, 159. 

 Mesorchium (jue'o-os ; o/>x ts , a testicle) A fold of peritoneum by which the 



testis is suspended, 206, 251, 298. 



Mesosoma (jueo-os ; au>/j.a, a body), in Molluscs The main body-mass, 111. 

 Mesotarsal, applied to an ankle-joint situated in the middle of the tarsus, 



241. 



Mesovarium (AKJO-OS ;* ovarius, adjective from ovum, an egg) -A fold of peri- 

 toneum by which the ovary is suspended, 207, 251. 

 Metabolism (/xETa/3o\7/, change) The sum total of the chemical changes 



which constantly occur in protoplasm, 6. 

 Metacromion, 280. 

 Metadiscoidal, 338. 



Metagenesis Simple alternation of sexual and asexual stages, 39. 

 Metamere = Segment, q.v. 

 Metamorphosis The series of changes by which a larval form becomes 



adult, 107, 122. 

 Metanephros (M eT , behind ; vt^pos, a kidney) The third-formed excretory 



organ typically developed in the Pigeon and Rabbit, 265, 316, 333, 334. 

 Metapleural, 136. 

 Metapophysis (fJ-era, in addition; a7ro<u<ris, a projecting part), in Vertebrae 



A process on the anterior end of the arch, above the prsezygapophysis, 

 273. 

 Metapterygium (M T "J after ; TTTsplyiov, a fin), 159, 160. 



