1024 The American Naturalist. [November, 
1868, and since then it has occupied a conspicuous place in the embry- 
ology of Teleosts.. .. The alimentary canal is formed by a process 
of folding, and Kupffer’s vescicle, as the terminal part of the postanal 
gut, follows the same method. After the gut has once been folded off, 
the homology of the vesicle with the postanal vesicle of Selachians 
is obvious. In each group the vesicle forms the dilated extremity of: 
the postanal gut, and receives, or would receive if it existed, the 
neurenteric canal... . But if Kupffer’s vesicle in its early stages 
indicates that the terminal portion of the archenteron was primitively 
dilated, we naturally inquire both for the causes and for a correspond- 
ing phenomenon in the ontogeny of those ainmals in which the 
archenteron is bodily transformed into the permanent gut. As to the 
latter point it would seem very common in the Amphibia for the archen- 
teron to be thus dilated. The existence of such a dilatation in the 
enteron of the primitive Chordata is further made probable by, and 
receives an explanation from, the relation of the neurenteric canal to 
the blastopore. It will be seen that in the interpretation of Kupffer’s 
vesicle I substantially agree with Cunningham: it is the terminal part 
of the archenteron. 
The most interesting addition to our knowledge is the author’s dis-. 
covery that the ear, branchial sense-organs, and organs of the lateral 
line arise from a common structure or embryonic “‘anlage.’’ ‘‘It 
been noticed in the trout that the anlage which was supposed to develop 
into the ear is remarkably long. Ihave found that this anlage not only 
gives rise to the ear, but to a functional branchial sense-organ and to 
the organs of the lateral line as well. Before the blastopore closes there 
is found behind the eye a long, shallow furrow [the sensory furrow] in. 
the nervous layer of the ectoderm. At two points the furrow begins 
to deepen, the deepening taking place downwards and inwards. At 
these two points the auditory sac and the branchial sense-organs will 
respectively be formed. ... A further stage in the development 
shows that the deepening of the furrow in the auditory and branchial 
sense-organ regions has continued until there are are two well-marked 
sacs, the anterior of which is the branchial sense-organ, the posterior 
the auditory sac. Between the two sacs persists the connecting ‘portion 
of the sensory furrow, and behind the auditory sacs the furrow is con- 
tinued for some distance. Zhe posterior portion of the furrow consti- 
tutes the anlage of the lateral line. 
‘The homology instituted by Eisig between the lateral line organs 
of fishes and the ‘seiten organ’ of certain Annelids is well known. 
Balfour, in his text-book, declined to accept it; and though Beard 



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