Dr. A. Korotneff on Polyparium ambulans. 22 L 



cavity ; further, we may assume the radial arrangement of the 

 septa to have disappeared, on the one hand, in consequence 



Fig. IV. 



Cross section of Cerianthus : m, muscles of the wall-lamina, 



of the division of the primary mouth-opening into a number 

 of secondary ones, and, on the other, on account of the extra- 

 ordinary elongation of the colony, and therefore what exists 

 in Pohjparium is to be regarded as regular. The free exis- 

 tence also has not been without influence ; for the performance 

 of the task of carrying out definite movements the parieto- 

 basilar muscle is converted into the transverse muscles 

 (transverse bands), and in this process corresponding" septa 

 of opposite sides must have met and become converted into 

 partition-like structures. In this way the radiate type of a 

 polyp may easily be converted into a bilateral type. In 

 order to make this metamorphosis intelligible the best way 

 is to have before us a transverse section of a Cerianthus 

 (fig. IV.) . If we imagine the buccal aperture in this divided, 

 the opposite septa, which approach so nearly as to touch at 

 the bottom of the inner gastral cavity, will necessarily grow 

 together*. 



* The comparison of Cerianthus with Polyparium is, however, the 

 more admissible, because, as has been shown, these forms are very simi- 

 lar histologically — for example, in this respect, that the wall in both cases 

 possesses a muscular and nervous layer. 



