164 BRODE. [Vo. XIV. 
its origin from the epidermis, its position between the dorsal 
and ventral muscles, its separation from the epidermis by the 
pushing in of muscles, and its connection with the oesophageal 
collar. He thinks that no such physiological importance can 
be ascribed to it, as in the fishes with its sense organs, but its 
morphological significance is unmistakable and perhaps greater 
than has yet appeared. 
Semper makes the very interesting observation that the 
origin of the eyes of Nais is confined to the lateral line, and 
raises the question as to the lateral trunk eyes of Polyophthalmus 
being also limited in their development to the lateral line and 
its transformations. 
Biitschli! misinterpreted Semper’s observations and supposed 
that the lateral lines of which he spoke were merely two of the 
many interruptions in the longitudinal muscle layer. 
Eisig 2 discusses the “lateral line” of Naids and comes to 
the conclusion that the homology instituted by Semper between 
this formation and the lateral line of vertebrates does not exist. 
His inference from the account of Semper’s discovery is that in 
Nais a problematic cell cord occupies a position similar to that 
occupied by the lateral-line system in vertebrates. 
Eisig’s reasons for concluding as he does are based on the 
fact that by the lateral line of vertebrates we mean the whole 
lateral-line system, and that Semper’s cell cord cannot be com- 
pared to any one part of the system. Semper’s intimation that 
it is comparable to the lateral nerve is not in harmony with 
what is known of the development of this organ in vertebrates. 
However, considering the fact that Semper found the eyes 
of Nais to occur in this line and thought it probable that the 
trunk eyes of Polyophthalmus would be found similarly situated, 
we must admit that he had some ground for making the com- 
parison. The “Anlage”’ of the lateral-line system is a cord of 
cells which grows down the side of the body and differentiates 
later into the different organs of the system. Now, if the lateral 
1 Q. Biitschli, Untersuchungen iiber freilebende Nematoden und die Gattung 
Chaetonotus, Zezt. f. wiss. Zool., Ba. XX VI, 1876, p. 401. 
2 Hugo Eisig, Die Seitenorgane und becherformigen Organe der Capitelliden, 
Mitth. a. d. Zool. Sta. Neapel, Bd. I, 1879, pp. 322-325. 
