536 WILLIAM BATESON. 
hypothetical groups has come to be the subject of some ridi- 
cule, perhaps deserved. But since this is what modern mor- 
phological criticism in great measure aims at doing, it cannot 
be altogether profitless to follow this method to its logical 
conclusions. 
That the results of such criticism must be highly specu- 
lative, and often liable to grave error, is evident. 
Part I.—Tue SrGMENTATION oF AMPHIOXUS AND THE VERTE- 
BRATA, COMPARED WITH THAT OF THE ANNELIDS. 
From the time when the theory of descent in some form or 
other became generally accepted amongst zoologists, the ques- 
tion of the pedigree of the Vertebrates has been the subject of 
much speculation and controversy. The amount of attention 
which has been bestowed on this question has perhaps,.been 
greater than is warranted by the actual importance BF the 
problem considered as a contribution to general biology; but 
when it is borne in mind that the question is that of the history 
of the human race, the fascination which has been found in it 
is not surprising. 
Beyond, however, this more sentimental side, there is 
another source of special interest to be found within the 
terms of the problem itself; namely, that which is afforded by 
the obscurity of the solution; for when the relation of any 
one group to the rest of the animal kingdom is sought, in most 
cases there are some cardinal features of anatomy common to 
it and to some other group, which appear to point to some 
affinity between them. For example, the structure of the 
Tracheata at once suggests Crustacean affinities, while there is 
a strong apparent resemblance between the whole Arthropoda 
and the Annelids. Even a group so isolated as the Mollusca 
has points of obvious harmony with other groups as soon as 
the characters of the Trochosphere are known, and similarly 
with most other groups. Hach and all of these “ obvious ” 
resemblances may be illusory, but still they furnish something 
