214 Dr. A. KorotnefF on Polyparium ambulans. 



as a thick cushion which runs transversely above the layer 

 of transverse muscles. The brothers Hertwig regard this 

 cushion as a fold-formation of the base of the septa caused 

 by the increased mass of the muscles here situated. The 

 parieto-basilar muscle is most strongly developed in Tealia 

 crassicornis, and in this form, according to the figures illus- 

 trating Hertwig's investigation *, we have a good right to 

 assume that the muscular fibres of the base of one septum 

 pass into the opposite septum. At any rate, we may assume 

 that at the meeting of the opposite septa the muscular cushions 

 pass into each other and give origin to a structure analogous 

 to the " transverse bands." 



It still remains for me to decide an important point which 

 relates to the relations of the septa and likewise of the muscles 

 to one another. We have already seen that in Polyparium 

 the inner chambers and intermediate chambers follow each 

 other alternately ; the inner chamber represents the gastral 

 space and the intermediate chamber the place where nQ.\Y 

 septa are formed. This alternating position is not without 

 relation to the muscular system. Hollard has already ex- 

 pressed the opinion that the longitudinal muscles which, in 

 transverse sections, are immediately recognized as thick pads, 

 are turned towards one another and enclosed in the central 

 chamber, while the transverse muscles, on the contrary, belong 

 only to the intermediate chamber. Ifw^e consider Pc»Z?/pamim 

 from this point of view we find the direct contrary; in this 

 form the longitudinal muscles (vertical muscles) belong to the 

 intermediate chamber, while the transverse muscles (" trans- 

 verse bands ") only occur in the internal chamber. In order 

 to explain this phenomenon we are compelled to submit the 

 principle established by Hollard to a rigid analysis. 



Rotteken and Schneider f have already indicated that two 

 pairs of septa in the body of the Actinia have really an ex- 

 ceptional position — these are the so-called directional septa 

 wdiich have a special significance for the orientation. These 

 septa are situated opposite each other, and have a particular 

 relation to the position of the buccal aperture and the oeso- 

 phageal tube : thus the buccal aperture possesses two angles 

 from which two deep grooves run down upon the inside of 

 the oesophageal tube ; the insertion of the directional septa 

 corresponds with the buccal angles and the grooves of the 



* O. and R. Hertwig, ' Die Actinien, anat. und bistol. Untersuclit ' 

 (Jena, 1879). 



t Schneider and Rotteken, '' Ueber den Ban der Actinieu und Koral- 

 len," in Sitzungsb. der Oberbess. Gesellscli., March 1871. 



