INDEX-GLOSSARY. 393 



Primitive .sheath The delicate membranous investment of a nerve-fibre, 215. 



Prismatic layer, 110, 125. 



Proboscidea, 346, 356. 



Process Acromion p., 250; Articular, 184; Clinoid, 273; Coracoid, 

 Coronoid, 183, 276 ; Costal, 238 ; Fronto-nasal, 329 ; Harnular, 275 ; 

 Iliac, 160; Mastoid p., 273; Maxillary p., 329; Maxillo- palatine, 

 234 ; Odontoid, 238, 279 ; Olecranon p., 186, 239, 281, 326 ; Orbital p., 

 233, 272; Palatine, 275; Par-occipital p., 272; Pterygoid p., 273; 

 Styloid p., 323 ; Supra-orbital p., 272; Transverse, 158, 184, 237, 278; 

 Uncinate p., 237 ; Xiphoid, 238 ; Zygomatic, 273, 275. 



Procoelous (irpo, before ; KoiXos, hollow), of the centra of vertebrae Con- 

 cave only in front, 184. 



Pro-echidna, 345, 353. 



Proctodeeum (TTPWKTOS, the rectum, the anus) The posterior part of the 

 alimentary canal which arises as an epiblastic pit ; the hind-gut, 48. 



Proglottis, 40-44. 



Promontory, 273. 



Pronation, of the fore-limb The position in which the palm is downwards 

 and the radius crosses the ulna, so that its distal end is inwards, 281, 

 326. 



Pronephros (TT/OO, before; ve^pos, a kidney), in Vertebrates The first- 

 formed excretory organ, which is usually very transitory ; the head 

 kidney, 166, 228, 265, 308. 



Pronucleus Male p., The name given to the nucleus of the sperm after it 

 enters the ovum, 74; female p. The nucleus of the ovum after the 

 formation of polar cells, 26, 74. 



Propterygium (TT/UO, before ; Tnepvyiov, a fin), 159. 



Prosencephalon (irpos, in addition ; cy/ce'0a\os, the brain) An outgrowth 

 or two lateral outgrowths of the fore-brain. See Fore-brain. 



Pro-scolex, 44. 



Prosimia-, 346, 357. 



Prostate An accessory gland on the male organs, 130. 



Prostomium (irpo ; CTTO'/LI, the mouth), 54, 75. 



Protection, 25, 178, 268, 312. 



Proteids (Ilpou-reus, a sea-god with remarkable power of changing his form) 

 Complex compounds of C, 0, N and H with small amounts of S and P, 

 58. 



Proteus animalcule = Amoeba, q.v. 



Protomerite, 17, 18. 



Protoplasm (Tr^w-ros. first ; TrXdoyxa, that which has been formed) An 

 extremely complex substance upon which life-manifestations depend, 6. 



Protopodite, in the CrayfishThe basal, undivided part of an appendage, 84. 



