' * 
158 Anton Dohm 
Hyoidarterie, nur um die frei gewordenen Gefäße der Spritzlochkieme 
wieder verwenden zu können? Und wenn so lange die dorsale Partie 
der Hyoidkieme die Wurzel der Carotis posterior bildete, wie kann 
plötzlich aus denselben Kiemenblättern die Carotis anterior interna 
hervorgehen? 
Die Antwort auf diese Fragen schuldet vor allen Dingen Prof. 
Gegenbaue, der mit seiner nicht motivirten Abweichung von Jon. 
Mullek' s klar dargelegter Auffassung die Materia peccans zuerst in 
diese schwierigen Fragen gebracht hat. 
Wie groß aber die Verwirrung geworden, wird sich erst zeigen, 
wenn ich jetzt dazu übergehe, die Verhältnisse der Teleosti er 
zu behandeln. 
3. Die Fseudobranchie und ihre Gefäfse bei den Teleostiern. 
Der erste Autor, welchen ich hier zu berücksichtigen habe, ist 
Balfour im 2. Bande seiner Comp. Enibryology p. 265 gelegent- 
lich einer Discussion der Vorfahrenschaft der Fische. Es heißt dort: 
»JVhile most of the structures supposed (by Dohm) to be re- 
mains of gill-clefts in front of the mouth do not appear to me to be 
of this nature, there is one organ which Stands in a more doubtful 
category. This organ is the so-called choroid gl and. The simi- 
larity of this organ to the pseudobranch of the mandibular or hyoid 
arch was pointed out to me by Dohm and the Suggestion was made 
by Mm that it is the remnant of a praemandibular gill, which has 
been retained owing to its functional connexion with the eye l . Ad- 
mitting this explanation to be true (which however is by no means 
certain) are we necessarily compellecl to hold that the choroid gland 
1 The probability of the choroid gland having the meaning attributed to it by 
Dohm is strengthened by the existence of a praemandibular segment as evidenced by 
the presence of a praemandibular head-cavity, the walls of which as shown by Mar- 
shall and myself give rise to the majority of the eye-muscles and of a nerve (the 
tlxird nerve cf. Marshall) corresponding to it; so that these parts together with the 
choroid glatid may be the rudiments belonging to the same segment. On the other hand 
the absence of the choroid gland in Ganoidei and Elasmobranchii, where a mandibu- 
lar pseudobranch is present, coupled with the absence of a mandibular pseudobranch 
in Teleostei where alone a choroid gland is present, renders the above view about the 
choroid gland somewhat doubtful. A thorough investigation of the ontogeny of the 
choroid gland might throw further light on this interesting question, bat I think it not 
impossible that the choroid gland may be nothing else but the modißed mandibular 
pseudobranch, a view which ßts in very well with the relations of the vessels of the 
Elasmobranch mandibular pseudobranch to the choroid. 
