12 



Allman, wlio has drawn special attention to this peculiar chitinous axial cord, (which 

 does not exist in any of the known Polyzoa), and has precisely derived from it his generic 

 appellation, calls it a ,,Blastophore" being of opinion that it is destined to bear the so-called 

 Statoblasts, which he represents as projecting from the posterior part of the contractile cord. 

 I regret that I cannot, from my own experience, give any decided opinion as to the axial cord 

 having likewise this destination, because I have not been able to observe the formation of 

 these so-called Statoblasts. 



Vital Phenomena. 



The animal, unlike the other Polyzoa, is very slightly sensitive, and is not much af- 

 fected by -having its tentacles or body touched. If the irritation is strong, it draws itself, but 

 only very slowly, and usually only a little way, back into its tube. This very slow and slug- 

 gish retraction, which may last a very long time before it ceases, contrasts strongly with the 

 extraordinary, almost lightning-like, rapidity with which the retraction takes place in the other 

 Polyzoa, and is evidently accounted for by the want of special retractor-muscles, and by the 

 slightly developed contractile elements, not distinguishable as evident muscular fibres, in the 

 contractile cord, the only instrument by which the retraction of the animal in the Ilhabdo- 

 pleura is effected. 



The extension (protrusion) of the animal is yet far more tardy than the retraction ; 

 the process is extremely slow and almost imperceptible; several hours may often elapse be- 

 fore the animal progresses from the stem or bottom of the cell to the aperture of the latter. 

 Neither do- we, as before remarked, find in the animal under consideration the slightest trace 

 of any special muscles for such progression; since the Endocyst, and also the parietal and 

 parieto-vaginal muscles connected with it are entirely wanting. The protrusion seems on the 

 other hand, as already mentioned, to take place in a very peculiar, and in the highest degree 

 remarkable manner, that is, solely by means of the enormously developed Epistome (Bucal 

 shield) which the animal uses strange at this may sound, as a sort of creeping organ, 

 like the foot, or creeping disc of the Gasteropods, to draw itself upwards little by little along 

 the wall of the cell to the aperture. 



Occurrence. 



The Rhabdopleura mirabilis seems to be a genuine deep-sea product, which I have 

 never found at a less depth than 100 fathoms; but it is probably to be found extensively at 

 greater depths, where it appears to be more and more plentiful. I have hitherto only found 

 it in Lofoten, where it is not uncommon, in soft clay bottom, at depths of 100 to 300 fathoms. 

 As the Polyzoarium is both very small and entirely colorless, it is rather difficult to discover. 

 Its presence is however easily detected by stirring the washed mud in a fine sieve with a 

 feather or another instrument, when irregular fibres will be noticed therein. These fibres, 

 covered with particles of mud, Rhizopod-shells and fragments of mussel-shells, will prove to 



