532 THE ORIGIN OF VERTEBRATES 
Parapodopsis, foot glands, 422 
Parathymus, 427 
Parathyroids, 427 
Parietal organ, 76 
Pecten of scorpion, 114, 359, 366, 371, 8372, 378, 374 
Pedipalpi, 190 
Periblast, 471 
Peripatus, 396, 399, 400, 411, 421, 429 
Petromyzon, alimentary canal, 405, 445 
- auditory organ, 378 
om branchial segments, 169 
“ life-history, 59 
‘i olfactory tube, 219, 226 
" pronephric duct, 402 
i retina and optic nerve, 95 
13 skeleton, 125 
% suctorial apparatus, 287, 304 
transformation, v. Transformation of the Lamprey 
Phagocytes, 420, 471 
Pharynx of Amphioxus, 410 
is Vertebrate, 440 
Phoronis, 439 
Phrynus, brain, 53 
as caudal brain, 450 
is carapace and carapace removed, 250 
#4 coscal diverticula, 109 
a operculum, 191 
‘ prosomatic appendages, 306 
crossing of dorso-ventral muscles, 271, 277 
stridulating apparatus, 368 
Phyllodeee, 395 
Phyllopoda, 321 
Pigment, in Ammoceetes, in position of atrial cavity, 412 
choroid of vertebrate eye, 104, 107 
tapetal layer of retina, 70 
white, of right pineal eye of Lamprey, 76, 80 
Pineal body, 14, 15 
eyes, 74, 233, 244 
Pr » of Ammoccetes, 80, 78, 85 
» gland, 63, 75, 456 
Pits, epithelial, of diaphragms in Ammoceetes, 164 
is skin in Ammoceetes, 173, 200 
Pituitary body, 244, 246, 319, 321, 425, 430 
Plasma-cells, 471 
Plakodes, 283 
Planarians, 475 
Plastron, formation of cranial walls from the, 86, 322, 341 
of Limulus, 136, 142, 143 
” 
” 
” 
evidence of segmentation of carapace, 249, 250, 341 
epithelial lining of central nervous system, 43, 457 
between glandular cells round brain of Ammoccetes, 211, 379 
Paleostracan, compared to trabecule of Ammoccetes, 145, 377 
