Wilder.] 178 [April 5, 



whether central or peripheral; of organisms which are low or high, 

 ancient or recent, immature or adult; and of their various attributes, 

 such as relative position, mode of development, chemical composi- 

 tion, size, form and color. 



The following diagram (p. 179) is an attempt to indicate in concise 

 form the work that has to be done in order to reduce our present con- 

 fused notions of zoological and anatomical relationship to something 

 like a logical coordination; it is essentially similar to one which was 

 presented three years ago, 58, Lect. 1, and I have not attempted to in- 

 corporate in it the new and valuable ideas of Lankester, 257, and 

 Mivart, 278. I am not now ready to state my grounds of differ- 

 ence from some of their views; and will merely express my gratifica- 

 tion at this sign of the recognition of what is to be done, by the new 

 and vigorous school of English anatomy. 



For analogy and the categories thereof, see Agassiz, 201, chap. 2, 

 sect, ix, 203, and the chapter on Morphology and Nomenclature, 200, 

 8, chap. 2, sect. I V. I shall confine myself to the discussion of homol- 

 ogies. 



Plural or Relative Homology. 



This is the relation between corresponding parts of different indi- 

 viduals; Geoffroy proposed to retain the term "analogie" for this 

 relation and to employ "homologie" only for what is here named sin- 

 gle or absolute homology ; but the two terms were used indiscrimin- 

 ately until 1846, when Owen, 20, 175, proposed the name "special 

 homology" for this relation, and "serial homology" for the other. Of 

 course the correspondence between the zoological criteria of Agassiz, 

 201, 261 and 272, and the anatomical criteria, is provisional until the 

 relative value of these criteria themselves is fully ascertained; but it 

 appears to me that some good may follow their simultaneous 

 presentation upon a diagram, even if it lead merely to a more 

 general admission of the principle of subordination of characters. 



I also venture to suggest that since the three higher groups are 

 based upon internal structural features and the three lower groups 

 upon external features, and since both plan, of structure and relative 

 position of organs, which are branch characters, and outline as deter- 

 mined by structure, and relative size of organs, which are family 

 characters, are all alike displayed upon a transverse (vertico-lateral) 

 section of the whole body, we may hereafter be able to say how the 

 other two sections, (latero-longal and vertieo-longal) correspond with 

 the criteria of the class and genus, the order and species, respectively 

 Some other questions in this connection will be discussed hereafter. 



