THE 
AMERICAN NATURALIST 
VoL. XXXI. November, 1897. 371 
CEPHALIC HOMOLOGIES. A CONTRIBUTION TO 
THE DETERMINATION OF THE ANCESTRY 
OF VERTEBRATES: 
By CHARLES Sepewick MInNot. 
PROFESSOR AT THE HARVARD MEDICAL SCHOOL, BOSTON, MASS, 
1. THE AFFINITIES OF AMPHIOXUS. 
That Amphioxus has affinities both with Tunicates and 
with Vertebrates is, with our present knowledge, quite clear ; 
but the relative degree of affinity on the two sides has not been 
settled. Amphioxus was originally classed with the fishes, 
but is now universally separated from them. Perhaps the 
most usual opinion is, that which classes Amphioxus with the 
Vertebrata, and divides the Vertebrata into two groups :— 
I. CEPHALOCHORDA, (Amphioxus). 
II. VERTEBRATA PROPER, (Craniota). 
This division recognizes the fact that Amphioxus differs 
fundamentally from all the true vertebrates, but holds that the 
concept “ Vertebrata” must be greatly extended and essen- 
tially modified, so as to admit the lancelet. The first writer 
known to me to deny that the Branchiostoma could be classed 
as a vertebrate was Carl Semper in 1875. This position has 
l Read before the British Association for the Advancement of Science, at 
Toronto, Canada, August 20, 1897. 
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