234 On the Evolution of the Vertebrata, [ March, 
consider ourselves as respectable and useful among man’s com- 
panions, and in our habits we would show the generations of cul- 
ture we have received. 
Leaving our plant and returning to human experience, we can 
summarize our view by saying that the problem of similarity of 
types with great structural diversity of kernel, is only soluble by 
influences which have had a very long period of time to work in; 
and the perfectness of the result attained is to be explained only 
upon the supposition of a very long period of intelligent selective 
action. It is very probable that a more intimate acquaintance 
with the facts concerning the development of a single domesti- 
cated plant, as gained from philological, physiological and re- 
corded data will some time or other tend to throw some light 
upon the antiquity of man and the direction and extent of his 
migrations. 
"rh 
VU 
ON THE EVOLUTION OF THE VERTEBRATA, PRO- 
GRESSIVE AND RETROGRESSIVE? 
BY E. D. COPE. 
( Continued from page 148, February number.) 
Ill. THE LINE OF THE UROcHORDA. 
$ | ined ee ue evidence ieads us to. anticipate that the 
primitive Vertebrata possessed nothing representative of the 
vertebrate skeleton beyond a chorda dorsalis. Above this axis 
should lie the nervous chord, and below it the nutritive and repro- 
ductive systems and their appendages. Such a type we have in its 
_ simplest form in the Branchiostoma, the representative of the di- 
vision of the Acrania. In the animals of this division the mouth 
and anus have the usual vertebrate position, at opposite ends of the 
body-cavity. The Tunicata (formerly referred to the Mollusca) 
are now known to present a still more primitive type of Verte- 
brata, to which the name of Urochorda has been given. These 
curious, frequently sessile creatures, have a vertebrate structure 
during the larval stage, which they ultimately lose. They have 
the necessary chorda, and nervous axis with a brain, and a cere- 
ae bral eye. They have at this time a tail, and are free-swimming ; 
peculiarity which a few of them retain throughout life ape 
oe p- 147, 2d line from bottom, omit “ Batrach 
1A lecture delivered before the Franklin se Jan. 16, 1884, (Erratum: on 
a”) 
