768 Affinities of Annelids to Vertebrates. [August, 
views, working mainly from the standpoint of comparative anat- 
omy, and drawing little or no material from the larval stages of 
annelids. His views may be briefly (and thus necessarily imper- 
fectly) stated as follows: Regarding the distinction of ventral 
and dorsal surfaces as of little morphological importance, we may 
make a direct comparison of annelid and vertebrate by supposing 
the mouth of the annelid to be a new formation, and that a mouth 
once existed upon the hemal (dorsal) side of the annelid which 
was homologous with the mouth of the vertebrate (Figs. I, 2). 
D 
‘| ae o 
M 7 y À 
Fic, 1.—Diagram of a vertebrate according to Semper’s view, showing relative 
positions of coche digestive tract, mouth (A) and anus (4); D, dorsal, V, 
ventral surfac 
Fic. 2.—Diagram of an annelid according io. bea M, mouth; 4, anus; 
M’, primitive mouth; D, dorsal, V, ventral surfac 
He draws close comparison between the muscles, nervous struc- 
tures apd excretory organs of the two groups, basing his views 
largely upon the study of the urogenital organs in the lower ver- 
tebrates and the process of asexual reproduction in certain oligo- 
chætous annelids. 
n these forms new individuals are Ered in chains by the 
appearance of budding zones across the body of the asexual 
_ parent, each of which zones gives rise anteriorly to the trunk of 
one zooid, and posteriorly to the head of the next following 
>  zo0did, so that two adjacent zones form a new individual between 
them, and parts of the new individual in front of the anterior 
-zone and behind the posterior zone. ‘As these individuals event- 
ually break loose as forms like the parent it is necessary that 
each” acquire a new mouth and cesophagus, supra-cesophageal 
eae and muscles. In the formation of these structures from 
STRT tissue and from more indifferent embryonic cells, 
