Dr. A. KorotnefF on Polyparium arabulans. 219 



occur in the septa; these are, 1, transverse bands, and 2, 

 vertical muscles. All these systems of muscles serve the 

 same purpose ; they provide for the locomotion of the animal. 

 The most important in this respect are the transverse bands ; 

 they shorten the transverse diameter of the polypary by 

 bringing the lateral parts of the body neai^er together ; with 

 the shortening of the transverse bands the body is extended, 

 which is accompanied to a certain extent by an elongation of 

 the longitudinal muscles. The weaker vertical muscles of 

 the septa play a subordinate part, performing a much less 

 onerous work ; they serve to pull up the acetabula from the 

 supporting body, which is the first act in the locomotion of 

 Polyparium. On further investigation of the processes of 

 locomotion in this creature we find that the liberation and 

 lifting of the acetabula certainly do not occur simultane- 

 ously throughout the whole length of the animal, but only at 

 a particular part of the colony — whether it is one transverse 

 row of acetabula, and therefore an intermediate chamber with 

 a transverse chamber, or agreater number of such segments that 

 is included, I cannot say with certainty, although 1 am in- 

 clined to think that only one segment is moved at once. 

 After the abbreviation of the transverse bands and the elon- 

 gation of the longitudinal muscles the acetabula separated 

 from the surface of support are pushed further, and this no 

 doubt goes on successively throughout the whole length of 

 the animal. This mode of locomotion cannot be called gliding 

 such as we observe in many Actinise, but a true walking^ as 

 the acetabula are to be regarded as feet, and in motion cause 

 an undulatory advance ; but as the acetabula are distributed 

 along the whole disk of the foot, and occur in considerable 

 numbers, the progression may be discriminated into separate 

 actions. 



It is not easy to determine the true taxonomic position of 

 Polyparium amhulans. The first impression that this form 

 produces is something quite peculiar, something that hardly 

 reminds us of any other form of Coelenterate. In summariz- 

 ing the different characteristics of Polyparium we shall speci- 

 ally note the four following points : — 1, absence of tentacles ; 

 2, occurrence of various buccal cones which lead into a com- 

 mon cavity without, however, possessing an oesophagus ; 3, 

 apparent absence of radial septa; and 4, occurrence of the 

 very peculiar partitions which divide the body of Polyparium 

 into segments. 



15* 



