of the Annelids and Vertebrates. 463 



directed upwards, which was suggested by Am])^re, Joh. 

 Midler, and Rathke, and even earlier by Meckel, led to the 

 recognition of a great agreement with the Vertebrates in the 

 origin and position of many organs, those Articulates which 

 were chosen for comparison (the Insects and Crustacea) were 

 precisely the ones which were not well suited to furnish the 

 proof of the correctness of the original view ; for no one had 

 succeeded in demonstrating the existence not only of the 

 above-mentioned resemblances, but also of actual agreement 

 in type of the Articulates and Vertebrates. 



The case is now, I think, different ; through the discovery 

 of segmental organs in the embryos of the Plagiostomes and 

 in many adult sharks *, I was led to suggest this process of 

 inversion once more— but as applied to an Annelid f, by 

 which was revealed a correspondence between Articulates and 

 Vertebrates far more complete in detail than that obtained by 

 the former direct comparison of Crustacea or of Insects with 

 Vertebrates. Nevertheless there were some difficulties ; and it 

 is natural that others should lay stress upon them in order to 

 demonstrate indirectly the unimportance of the extensive re- 

 semblances, first pointed out by me, in the typical structure of 

 an Annelid and of a Vertebrate embryo. 



The following preliminary communication is intended to 



* See ' Annals and Magazine of Natural History,' ser. 4, vol. xv. p. 94. 



t I should like to suggest that a slight lapsus calami occm-red to our 

 revered master Baer when he lately, in his notice of Dohrn's and my 

 works, represented the facts incorrectly : it is not the former who was 

 the first to compare the inverted worm-sections with transverse sections 

 of a Vertebrate embryo, and the organs of both with one another respec- 

 tively, but I ; and this was not done by me incidentally, but completely 

 and with the addition of fio-ui-es. My first preliminary communication 

 upon this subject appeared in July 1874, and the larger memoir (' Die 

 Stammverwandtschaft ' &c.) in October 1874 ; while Dohrn's work first 

 appeared in February or March 1875. 



It must be admitted that this investigator goes further than I in his 

 hypothetical conclusions ; thus he loses himself in specialities which can- 

 not be proved and are completely devoid of substantial foundation ; 

 while I stop at the proof of the identity in relative position of ahnost all 

 the organs of the Annelids and of the vertebrate embryos. But this I 

 must claim as my property, to the acquisition of which no earlier expres- 

 sion of Dohrn could have led me ; while it remains doubtful whether 

 Dohrn would have taken an annelid as his starting point if he had not 

 been acquainted with my work before publishing his own. It is true that 

 he claims {I. c. p. iv) to have intimated, in the preface to the second part 

 of his paper on the structure and development of the Arthropods, that 

 " to him it was not so much the Ascidians as the Annelids which seemed 

 to be the Invertebrates standing nearest to the Vertebrates." In the pre- 

 face to the second part, however, there is no mention of this, and j ust as 

 little in his other articles on the Crustacea. In the introduction to the 

 third part (Jenaische Zeitschr. Band v. p. 278), where he first treats of 



