737 



als em sackförniiges, nngefalir 3 in.m. langes Gebilde aus dem 

 Biiideuewebe fiei prapariren, seine Wande zeigten sioh ansserordeiit- 

 lic'li (liciil iind inwendig glall, da« Epitlielinm liocli mid drüsig. 

 Ebenso zeigte sicli der dorsale Anliaiig von Heptanclins, abei- lelativ 

 noch kürzer". As it wil! presenllv l)e been, lie nndonbtedlv dissected 

 out llie sense organ bladder. 



Hoffmann (1899) inter alia also investigated tlie development 

 of the diverlicnlnni of the spiracle in Acantliias. He found it to 

 make its a|)pearance first in 28 m.m. long embryos and innervated 

 bv a brand) from tiie lateral line system of the facial nerve. 



He considers this branch, which also supplies epidermal sense 

 organs, most likely homologous to the ram. olicns of the Ganoids. 

 The diverticulum is soon directed forwards with its blind end. and 

 unites itself there with the nerve. I can confirm this from my 

 material of Acantliias. 



Hoffmann discovered the innervation, well knowing of the work 

 of Wright, from wliich he (|uotes in detail. He. however, missed 

 the conclusion that a sense organ had to be present. He was too 

 much under the impression of ha> ing here lo do with the vestigial 

 part of a branchial |)oucli. wlncli had disappeared. 



Besides the (wo embrvos of Heptanchus, my own investigation 

 also includes a series of sections (15ti thick) through embryos of 

 Acantliias varying in leiiglh from 23 lo 98 m.m. 



In ilie 23 m.m. long embryo, ilie anterior wall of the spiracle 

 forms a rostrally directed diverticulum, next to the auditory organ, 

 from which it is separated by (he jngnlar vein (the nervus facialis 

 running under the veinj. The iii\ eriiculnm is to be seen on 7 sec- 

 tions anterior lo the external opening of the spiracle, and has the 

 shape of a cone flattened on one side, the axis of which runs 

 parallel to the longitudinal axis, |)assiiig ihrough the notochord. The 

 thiee anterior ones of the seven sections pass through the top of 

 the cone, which is distinguished by its columnar epithelium, so that 

 the lumen appears for llie first lime on the third section. One also 

 sees the termination of the branch of the ram. olicns connected 

 here lo the group of the columnar cells. Hoffmann already pointed 

 out, that one could stipulate, thiough this connection the situation 

 of the organ before it is more clearly defined. 



A cross section llirough the anterior margin of the external opening 

 of the spiracle on the skin at the same time passed through the 

 internal opening towards the iniesline in an embryo of 39i m.m. 

 of which I in 1922 described llio slcnll. The diverticulum is to be 

 seen (in 21 seclions losUalwards. Jiisl as in llie embryo of 23 m.m. 



