Wilder.] 160 [April 5, 



problem which had so long existed as a mystery for the morphologist," 

 Professor Huxley admits that "it cannot be considered as thoroughly 

 satisfactory since it has not been checked by the aid of the complete 

 study of the development of the parts in question, the only method 

 by which any morphological problem can be determined." The pre- 

 cise value of development in the determination of homologies will 

 be discussed hereafter, but there can be no question that too little 

 importance had been given to it in previous comparisons of the 

 membra. 



"■ Professor Huxley instituted a new comparison of the limbs, placed 

 not in the position which they assume in adult life, but in the only 

 one in which they really correspond with each other, viz., that which 

 they first exhibit in the embryo. In this condition they stand out at 

 right angles from the body, the extensor surfaces being placed dor- 

 sally, and the flexor surfaces ventrally, with both pairs of limbs. 

 They then gradually become bent and afterward acquire the modified 

 position which suits them for their function in life, and to which their 

 various articulations become adapted. The embryonic position con- 

 tinues throughout life in many amphibia and reptiles and without 

 much change in galeopithecus." 



Huxley then proceeds to compare the premembral (anterior) borders 

 of the membra together, making the radius and pollex homologous 

 with the tibia and primus, upon the generally accepted principle of 

 syntropy or serial homology; not realizing that the very same regard 

 for the facts of development which led him to ignore the subsequent 

 flexure and attitudes of the membra, should also require him to give 

 no heed to those secondary modifications of the primordial buds 

 which differentiate pollex and primus from their fellows, and cause 

 them to resemble each other in many higher animals ; but aside from 

 his special interpretation of homologies, I am now ready to accept his 

 method of placing the membra for comparison as the true one, of 

 which more hereafter. 



This general view of the method to be pursued in determining 

 intermembral homologies has been adopted by Mivart in 1866, by 

 Pagenstecher in 1867, by Eolleston in 1868, and by Flower in 1870; 

 who, however, have each proposed modifications in detail, which I 

 will not discuss here, since the special interpretations of muscular 

 homologies depend upon the general view of membral homology, and. 

 stand or fall therewith. 



Parker has not expressed a decided opinion upon the subject; let 



