The Columella Aiiris in Ainpliibia. 561 



the tip of the stilus is likewise of cartilage. This description of the 

 condition in Siredon corresponds fairly well with the relations of the 

 columella in Ambystoma before transformation. The names ap- 

 plied to the structure varied : Operculum (Wiedersheim) ; Columella 

 (Hasse) ; Stapes (Parker). Windischmann ('31), whose paper we 

 have not been able to examine, described in Siredon a stilus whose 

 (fenestral) plate he termed Patina, while behind the Patina there 

 was an Operculum cartilagineum joined with it only by connective 

 tissue. This description of Windischmann's was discredited by later 

 workers. It is probable, however, in view of the possibility that 

 many, perhaps most, of the so-called Siredons were larval Ambys- 

 tomas and not super-larvse (Axolotl) that Windischmann correctly 

 described the condition in a transforming individual. More recently 

 Iwanzoff ('94) describes the condition in Siredon as follows, appar- 

 ently erring in ascribing the connection of the columella with the 

 squamosum to the operculum : 



"Bei Siredon befestigt sich der Musculus protrahens scapulae mit 

 seinem proximalen Ende am rundlichen Knorpel auf der hinteren 

 Wand des Schadels. Parker und Wiedersheim ha] ten diesen Knorpel 

 einfaeh fiir einen Teil des Knorpelschiidels, um so mehr, da er 

 schwach von dem letzteren abgegi-enzt ist. Aus dem nachgewiesenen 

 Grunde nehme ich ihn fiir den Stapes, um so mehr, als er demselben 

 audi nach seiner Lage entspricht. Desshalb ist der Teil, welchen 

 die genannten Autoren als Stapes annehmen, namlich die teils 

 knocherne, teils knorpel ige nnd bindegewebige Bildung, die vom 

 Stapes zum Quadratknorpel und Squamosum, und dieselbe Lage, 

 wie das Rand mit den Columellarknochelchen bei Pelobates hat, fiir 

 die Columella zu halten. Anf diese Weise erscheint die gewohnliche 

 Behauptung, dass Ix^i den Urodelen die Columella gar nicht existirt, 

 fiir Siredon nnd einige andere Formen, irrthiimlich." 



Iwanzoff seems, therefore, to have seen two structures, though their 

 detailed relations were confused. The early description of Windisch- 

 mann portrays most closely the condition in Ambystoma, thongh all 

 the descriptions were doubtless approximately correct if the age 

 (larval or adult) is considered. No one seems to liave recognized 

 the fact that the condition changes with age. 



