102 ZOOLOGY DIRECT IONS 



Transverse section — A section taken at right angles to the main 

 axis of the body. 



Trlchocysts — Minute, rod-like refractive bodies in ectoplasm of 

 some ciliates. 



Umbo — The protuberance of a bivalve shell above the hinge liga- 

 ment. 



Ventral — "The under side of the body;" or more strictly that 

 part of the body directed toward the surface upon which the 

 animal walks or comes to rest. 



Vertical section — A section running from dorsal to ventral sur- 

 face through the main or chief axis of the body. 



Vestigial — Any organ or structure which never reaches full de- 

 velopment and is consequently without function. 



Wing-pads — Rudimentary, sac-like wings on the thorax of many 

 nymphs. 



X — preceding a number, indicates the number of times your 

 drawing is to be greater than the dimensions of the original 

 specimen. 



Zooid — One of the individuals in a united colony of animals. 



Zygote — A single cell resulting from the fusion of two gametes. 



