CONTEIBrJTION TO KNOWLEDGE OF EHAEDOPLEUEA. 639 



on a mother branch ; sometimes two or even three successive 

 polypide-buds become proliferous^ and then as a result we have 

 the appearance of three or four branches diverging from an 

 approximately common point. 



In all cases the buds have to burst through the side of the 

 chamber of the tubarium in which each is enclosed. The 

 process has recently taken place in the instance of the polyp e, 

 fig. 1, PI. XXXIX. Upon the side of the axial tubarium thus 

 ruptured the young polypide now constructs its own polypide- 

 tubcj at first recumbent and then upright. Thus it comes 

 about that to every polypide there is an axial tubarium cham- 

 ber, and a long tube opening into it at an angle. 



Statoblasts or Hybernacula. — Allman has described 

 what appear to be arrested buds which have not burst through 

 the wall of the axial tubarian chamber as statoblasts. They 

 appear to have been unusually numerous in Allman's specimen. 

 It does not seem to be useful to apply the name " statoblast " 

 to such arrested buds, because the true statoblasts of Phylac- 

 tolsema have a totally difi'erent origin and position — are in fact 

 produced within the body cavity, and have no relation to 

 ordinary buds. The name " hybernacula," applied already to 

 the arrested buds of Paludicella, would be more appropriate. 

 I have come across several instances of such arrested 

 buds in Rhabdopleura, but have no evidence to show that 

 they will ultimately proceed to development, nor that their 

 formation is due to anything more than an abnormality and 

 distortion of the regular growth (PI. XLI, fig. 6). Occasionally 

 (as has been pointed out before) one finds not merely that a bud 

 is arrested, but that it dies and decomposes without breaking 

 its way out through the wall of the axial chamber of the 

 tubarium (fig. 2, PL XLI). These " closed chambers," as Sars 

 terms them, do not seem to have any regular distribution or 

 functional significance. I should regard them as cases where 

 the strength of the tubarian wall accidentally proved too much 

 for the resources at the disposal of the young polypide in its 

 attempt to break through ; and very possibly the hybernacula 

 are of similar origin. A remarkable instance of arrested buds 



