GLOSSARY. 63 



Holotrfcha (Gr. holds, whole ; thrix, trichos, hair). A group 



of the Ciliata in which the cilia are scattered all over the 



body, and are of the same kind. 



Homocer'cal (Gr. homoios, like; kerkos, a tail). A term ap- 

 plied to the tails of fishes when the tail lobes appear to be 



arranged symmetrically to the axis of the body. 

 Homceosau'ria (Gr. homoios, similar; sauros, a lizard). A 



group of extinct lizard-like animals belonging to the 



Lacertilia. 



Homo'logy (Gr. homos, the same; logos, proportion). Simi- 

 larity in structure, as contradistinguished from similarity 



of function. 

 Homo'typy (Gr. homos, the same; tupos, a type or model). A 



term suggested by Owen to be applied instead of serial 



homology, or the similarity of parts serially repeated in the 



same animal. 

 Horop'ter (Gr. horos, a boundary, limit ; opsts, sight). A line 



or surface in the field of vision, for any given position of 



the eyes, such that the images of the points in it all fall on 



corresponding points of the retina. 

 Hu'mero-abdomina'lis. A muscle passing from the humerus 



to the abdomen in the hedgehog. 

 Hu'mero-dorsa'lis. A muscle which in the hedgehog passes 



from the humerus to the integument of the back. 

 Hu'merus (L. the bone of the upper part of the arm). The 



bone of the upper segment of the anterior limb in the 



Vertebrata. 



Hu'nrns (L. soil). Soil formed of decomposed organic material. 

 Hy'aline ") (Gr. hyalos, crystal ; eidos, shape). Clear as crystal ; 

 Hy'aloid j applied to a variety of cartilage. 

 Hy'dra (Gr. hudra, a water-dragon). The fresh- water polype 



belonging to the Hydrozoa. 

 Hy'dranth (Gr. hudra, a water-dragon ; anthos, a flower). 



The sac in the Hydrozoa which opens at one end into the 



digestive cavity. 

 Hydroe'cium (Gr. hudra, a water-dragon ; oikos, a dwelling). 



A small chamber at the posterior end of the anterior 



nectocalyx in some Siphonophora. 

 Hydro'phora (Gr. hudra, a water-dragon ; phoreo, I bear). 



A group of the Hydrozoa. 

 Hydrophyl'lia (Gr. hudra, a water-dragon ; phullon, a leaf). 



The protective coverings of the hydranths in some 



Hydrozoa. 



