278 GLOSSARY. 



Haustellum. The suctorial proboscis in the Diptera. 



Hectocotylus. One of the arms of a cuttle-fish modified into a 

 reproductive organ. 



Hemelytra. The upper or anterior wings of Hemipterous insects. 



Hemimetabolio. Incomplete metamorphosis. 



Heredity. The tendency (mental or physical) which asserts itself 

 in successive generations. 



Heterocercal. When the upper and lower lobes of the tail of a 

 fish are dissimilar. 



Heteroplast. The dissimilarity in the cells of a group of tissues, 

 as in muscles, nerves, &c. 



Heteroplasty. "The method whereby physiological division of 

 labour is accomplished " (Macalister). 



Hexicoloyg. The study of the inter-relations of animals. 



Hippocampus minor. An elevation in the posterior oornu of the 

 lateral ventricle of the brain. 



Histology. The minute anatomy of the tissues. 



Homocercal. When both lobes of the tail of a fish are alike. 



Homogeny (Bay Lankester) Similarity of structure due to de- 

 scent from a common ancestor. 



Homologue. Identity of an organ in different animals under every 

 kind of form and function. 



Homomorphous. Having the same form. 



Homoplast. A structure which is supposed " to have grown 

 alike in obedience to the influence of similar external causes 

 acting on similar innate powers " (Mivarf). 



Homoplaxy (Eay Lankester). Similarity of structure due to 

 adaptation. 



Homotypes. Analogical parts. 



Hydatid. A pathological product, caused by entozoic worms, 

 consisting of a cyst containing a watery fluid. 



Hydranth. See Polypite. 



Hydra-tuba. One of the earlier forms of certain Hydrozoa de- 

 veloping buds, and passing into the " Scyphistoma "-stage. 



Hydrocaulus. "All that portion of the hydrophyton which in- 

 tervenes between the hydrorhiza and the hydranth " (Allmati). 



Hydrocysts. Peculiar sacs which, with " groups of gonophores, 

 are borne upon a common stem, and constitute a gonoblasti- 

 dium or blastostyle." 



