112 A. OKA. 



polypide, which is obviously of grentest physiological iiiiport;iiice, the 

 fibres are smooth. In marine Polyzoa, however, I have observed 

 that the muscles of the avicularia and the vibracula are striated. 



The muscular fibres belonging to the funiculus run longitu- 

 dinally on the inner surface of the basement membrane, on which the 

 cellular wall of the funiculus rests (fig. ol, PL XIX). They run 

 separately without forming bundles, and present the same appearance 

 as those of other parts. Their extreme fineness as well as their small 

 number agrees with the fact that the funiculus contracts, if ever, 

 in a very limited degree. 



The muscles running between the cystidal wall and the bottom 

 of the invaginated fold (at the junction of the cystidal and the poly- 

 pidal endocyst) are called the Parieto- vaginal muscles (fig. -1, PI. 

 XVII, M"). Their fibres run either solitary or in bundles, forming 

 on an average 13-14 sets arranged somewhat radiall}'. Their points 

 of attachment to the cystidal Avail is irregular. These sets of 

 muscles cause the presence of the invaginated fold of the body-wall. 

 In i'6'c'f. (jdatinosa when the polypides fully expand, this fold, 

 which is otherwise distinctly present, disappears, the muscles relax- 

 in o' to their full extent. 



The great retractors of the [)olypide consist of a pair of well 

 developed muscular bundles, right and left in the perigastric cavity 

 (fig. -1, PI. XVII, Jl/^^^). The fibres are modifications of the muscular 

 layer of the endocyst, extraordinarily developed to serve their special 

 purpose. The point of attachment of each bundle to the bottom (^f 

 the cystid is siiigle, but the upper portion is split into a large number 

 of smaller bundles which are inserted into the walls of the œsophagus 

 and the stomach at various places, but most numerously at the 

 upper part of the former. The bundle is ensheathed in a sort of fine 

 sarcolemma, which could distinctly be demonstrated at such places 



