1897.] Cephalic Homologies. 943 
of the Dohrn-Semper Annelid theory of the origin of Verte- 
brates, which at present are the most serious. 
One more point, the cephalic homologies advocated increase 
the morphological importance of the eyes, and further empha- 
size the divergence between Amphioxus and Vertebrates, and 
makes the absence of lateral eyes in Amphioxus more signifi- 
cant even than before, and affords a further justification for 
the union of Amphioxus with the Tunicata. 
I have presented the subject in the merest outline, for al- 
most every sentence might be expanded to a paragraph, often 
into a chapter, without making the treatment exhaustive, but 
I hope enough has been said to make the argumentation clear 
and to justify it. 
The origin of Vertebrates is one of the most difficult and 
obscure problems which at present occupy the general atten- 
tion of zoologists. I am well aware that my own studies have 
concentrated upon the embryology of Vertebrates, and that it 
is difficult, perhaps, impossible, for one man to have a first 
hand mastery through his own observations of all the evidence 
which must decide the final solution. I have expressed, there- 
fore, not convictions, but probabilities, and must certainly 
reserve the right to adopt other conclusions than those above 
advocated. The rival theories have sometimes taken on a 
very positive tone, and their advocates have referred to the 
Dohrn-Semper theory as a thing of the past, discarded and 
quite disproved. This attitude is regrettable, and I hope, by 
showing that much can still be said in favor of the origin of 
Vertebrates from Annelids, to contribute towards a sober and 
judicial discussion of an important and interesting topic. 
8. CONCLUSION. 
It remains only to present the following simple and com- 
prehensive phylogenetic table :— 
Tunicata 
ss manera 
Metlonte 
Annelida—Protochorda—— “~~~ Amphioxus 
“~ Vertebrata 
64 
