INDEX 



X ellow cells : of Radiolaria, 

 299 ; of Earthworm, 523, 327, 332 



Yolk, yolk-granules or spheres, 195, 

 546 ; and see under various 

 types 



Yolk-cells, 200, 202 



Yolk-plug, 201 



Yolk-sac, 454 



^ooid, 281 ; and see Megazoold 



and Microzooid 

 Zoology, I ... 



Zoophytes, see Hydroid polypes ' 

 Zooxanthella, 299 

 Zygapophysis, 36, 481 

 Zygoma : zygomatic arch, 477^ 478 

 Zygote, 197, 279 



MAUD CI.AV AND SONS, LIMITED, LONDON AND BUNGAV. 



