of the Term “ Homology.” 119 
which arise similarly, whether they descend from the same 
ncestral homogens, č. e. homogenetie homologues which 
do not arise similarly, though probably descended from common 
ancestral parts, e. g. the legs of flies of diverse development. 
- Homoplastic homologues, 7. e. parts closely similar as to 
relative position, but with no genetic affinity, or only a remote 
one, e. g. the ventricles of a bat and a bird. 
Homogenetic serial homologues, 4. e. different parts of 
one individual, the correspondence between which is to be 
accounted for genetically, e. g. perhaps any two somites of the 
abdomen of a lobster (?). 
8. Homoplastic serial homologues, 7. e. different parts of one 
individual, the correspondence between which is to be ac- 
counted for by the influence of external conditions (the * su- 
perinduced segmentation" of Mr. Herbert Spencer), e. g. the 
fore and hind limbs of one side of any mammal. 
9. Vertical homologues, 7. e. different corresponding parts of 
one individual, of which one part is dorsal the other ventral, 
e.g. dorsal and anal fins of certain fishes. 
10. Lateral homologues, i.e. different corresponding parts 
of one individual, of which one part is right and the other left, 
€. g. the right and left arms of a man. 
11. Antero-posterior homologues, t. e. different corresponding 
parts of one individual, of which one part is anterior, the other 
posterior, e. g. the mouth and the cloaca. : 
12. Radial homologues, 7. e. different corresponding parts of 
one individual which radiate from a central axis, e. g. any two 
arms on the same starfish. rd 
13. Homotrophic homologues, 4. e. parts of an individual 
the correspondences between which are regarded as due to in- 
ternal modifying influences, e. g. the eyes and the ears. 
14. Serial homotrophes, 7.e. homotrophic homologues the 
correspondence between which is antero-posterior, e. g. an extra 
thumb and an extra great-toe on the same side of the same man. 
15. Vertical homotrophes, ¢. e. homotrophie homologues 
which correspond vertically. : 
16. Lateral homotrophes, 4. e. homotrophie homologues of 
the two sides of one individual, e. g. the nt and left eyes. 
17. Antero-posterior homotrophes, 7. e. homotrophic homo- 
logues which correspond antero-posteriorly. . Seog 
18. Actinologous homologues, ?. e. successive subdivisions, 
parts, or regions of a part or segmented organ, e. g. two suc- 
cessive joints of an antenna of a lobster, or the vertebral and 
sternal parts of the same costal element. 
