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GLOSSARY. 



Abdomen. The cavity containing the intestines. 



Abiogenesis. The production of living organisms without pre- 

 existing germs. 



Acephalous. Having no head. 



Acetabula. The suckers on the arms of a cuttle-fish. 



Acetahulum. The cavity which receives the head of the thigh- 

 bone. 



Ac&lous. Without an intestinal cavity. 



Acontia. See Craspeda. 



Acrocyst. " An external sac which in certain hydroids is formed 

 upon the summit of the gonangium, where it constitutes a 

 receptacle in which the ova pass through some of the earlier 

 stages of their development." (Allman^) 



Acrodont. The attachment of a tooth by its base to the edge of the 

 jaw. 



Acromyodic. When certain muscles in birds are attached to the 

 end of the bronchial semirings of the syrinx. 



Actinomeres. The lobes lying between the ctenophores of an ac- 

 tinosoma. 



Actinosoma. The body, simple or compound, of an Actinozoon. 



Actinula. " The locomotive polypoid embryo into which, in cer- 

 tain genera (of Hydroida), the egg becomes directly developed." 

 (Allman.) 



Aculeus. The sting of bees, wasps, &c. 



Adaptation. The variation which tends to fit an organ for the 

 part it has to perform, or to enable it to meet new conditions. 



Adelocodonic. The condition of a gonophore when no developed 

 umbrella is present. 



JEtiology. The study of physical causes in the origin and de- 

 velopment of organized beings. The "doctrine of efficient as 

 opposed to final causes." 



Agamic. Non-sexual reproduction. 



