RHABDOPLEURA MIRABILIS. , 35 



seems to go over into the tliiu skin which encloses the 

 digestive apparatus. Its ventral fibrous part may still be 

 traced (see fig. 1) to a considerable distance forward, in the 

 form of a rather wide, clear skin border, which gradually 

 disappears in front of the cardia. In this skin border the 

 fine longitudinal fibres may still be distinctly observed 

 diverging like radii ; but I was not able to trace their course 

 further. The posterior end, which, as beforesaid, is attached 

 to the axial cord at the bottom of the chamber in the 

 stem which corresponds to the cell, is somewhat enlarged ; 

 and all through of a very distinctly marked cellular structure, 

 without any evident fibre. In spirit specimens the con- 

 tractile cord shows itself often irregularly thickened in 

 particular places, and is also thus represented in Allman's 

 figures ; but this appears to be only a result of the action of 

 the spirit. In living exemplars I have always found it, 

 whether fully extended or contracted, of a cylindrical form. 

 When the polypide, as is frequently the case, is very strongly 

 retracted, not only to the bottom of the free cell, but also 

 partly in the corresponding chamber of the stem, the con- 

 tractile cord is always spirally convolved, so that the coils 

 are closer or looser, accordingly as the retraction is stronger 

 or weaker (see fig. 6). Also when, after severing the con- 

 tractile cord at its base, we take the animal out of its cell, 

 the cord always convolves itself in spiral coils, 



Allman has considered this contractile cord as correspond- 

 ing with the so-called funiculus in the ordinary Polyzoa, 

 although it is not, as in these, attached to the end of the 

 stomach (the terminal csecum), but on the ventral side of the 

 polypide^s body (Allman has represented it erroneously 

 as attached near the end, on the dorsal side). Moreover, 

 Allman indicates that this funiculus is accompanied by a 

 long fascicle of muscular fibres, attached to the chitinous 

 cord (axial cord) at the point where the funiculus is joined 

 to the same ; and that at the point where the funiculus is 

 joined to the animaFs body, this muscular fascicle divides 

 itself in two bands, of which one goes along the right side, 

 and the other along the left side of the body, finally attach- 

 ing themselves, each on its own side, to the pharynx below 

 the lophophore. These fibres form, according to Allman, 

 the great retractor muscles of the polypide. This representa- 

 tion, which in fact only depends on spirit specimens, does 

 not, as may be seen, agree with what I have had occasion to 

 observe in our northern species, in which the fascicle of 

 muscles (if one really may venture to use this appellation 

 here) is everywhere^ as an integral part, intimately con- 



