RELATION OF THE NEMERTEA TO THE VERTEBRATA. 641 



departure made by those who are interested in the phylogeny 

 of the Chordata. In due time arduous and detailed morpho- 

 logical investigations on the Platyelminthes in general, and on 

 the Nemertea in particular, may then lead us to more satis- 

 factory conclusions than are the fata morgana that are so 

 temptingly evoked before our eyes by the ingenious manipula- 

 tions of the indefatigable founder of the first and foremost 

 Zoological Station, when, following his lead, we find ourselves 

 wandering in the barren deserts of that province of phylogeny 

 in which he attempts to establish a close connection between 

 Chordata and Annelida. 



All these considerations have induced me to give this rapid 

 outline sketch of the degree of comparison which I hold to 

 exist between Chordate and Nemertean (more especially Palaeo- 

 nemertean and Schizonemertean) nervous systems, although I 

 am perfectly aware that there is a growing tendency among 

 those authors at present occupied with questions concerning 

 the morphology of the Vertebrate nervous system (Froriep, 

 Baldwin Spencer, Beard, Cunningham, Kleinenberg, and many 

 others) to accept Semper's and Dohrn's views of the Annelidan 

 descent of Vertebrates. Wiedersheim, in the new edition of 

 his ' Vergleichende Anatomic' (1886), does not even hesitate 

 to bring these results in their unripe phase before the more 

 extensive public of students, and this generally in acquiescent 

 terms. It is curious to see how, e.g. the question of the 

 cephalic nerves and their comparison to spinal nerves, that 

 of the nerve-roots, the cephalic ganglia and their respective 

 connecting trunks, have given occasion to the most diverse 

 twisting and retwistiug of the facts in order to bring out a 

 fixed scheme or diagram, which might then be compared to 

 what obtained in Annelids, and in which the highest degree of 

 similarity between the respective somites might be obtained^ 

 thus establishing a preconceived idea of the Vertebrate ancestor 

 as a most rigorously segmented animal. The value of these 

 speculations has been already tested above, and I may be 

 allowed once more to express my conviction that our com- 

 parisons between the Chordata and their lower Invertebrate 



