15 



and behind this union there appeared ah'eady an evident incurvation or incision in the l)ody 

 of the Polypide as the first indication of the Inical orifice. That the large scutifonn plate is 

 the homologon of the hucal shield in the fully developed Polypide is sufficiently evident, both 

 from its position relatively to the animal's body and from its shape. Alhnan has also recog- 

 nised this; however when he assimilates this plate in the Rhabdopleura-buds with the mantle 

 lobes of the Lamellibranchiata, the notion seems to me very hazardous and difficult to esta- 

 blish. In any case, the early appearance and enormous development of this part in the buds 

 of the Rliabdopleura, are extremely remarkable. 



Allman has — guided especially by the mode of development in the Rhabdopleura — come 

 to the conclusion that the Polyzoa are not, as was formerly imagined, most nearly related to 

 the Brachiopods, but to the Lamellibranchiata, and gives 1. c. some schematic figures, in order 

 to represent more evidently the agreement of the Rhabdopleura-buds with a Lamellibranch. 

 Allman however presupposes, as taken for granted, that the Rhabdojjleura is furnished with 

 an endocyst of the same nature as the other Polyzoa, which, as above stated, is not the 

 case; as also his conception of the bucal shield seems to be inaccvu-ate. 



As will be seen in the sequel, my Father has acquired a very ditferent notion with regard 

 to the relationship of the Polyzoa; for — guided by the organisation of their lowest represen- 

 tative, the Rhabdopleura, — he has arrived at the surprising conclusion that the Polyzoa in all 

 probability have taken their origin from the Coelenterates, namely tlie Hydrozoa. 



Like Allman, I sometimes found in the middle of the stem of the polyzoarium indi- 

 vidual chambers which, without containing any bud in process of formation, were quite closed 

 and not continued into any cell (see fig. 1.3). The inteiior wall of these chaml)ers was always 

 of very dark horn-brown color, and so little transparent that the axial cord, also here running 

 in the middle, was but dimly discernible through the wall. This dark color was particularly 

 intense at one of the ends, and appeared to proceed from the axial cord fixed in the middle 

 of the septa, and here somewhat enlarged. Its exterior horny substance seemed to be directly 

 continued into the adjacent chamber of the stem. Allman considers these closed chambers, 

 wherein he has thought to perceive a stratum of large polygonal cells, — of which however I 

 have not been able to observe the slightest trace in any that I have examined, — as Statoblasts, 

 and thinks that they are formed by the posterior enlarged part of the contractile cord. This 

 seems to me however to be far from probable, at least in reference to the closed chambers 

 examined by me; for they looked far more like remains of old cells decayed, owing to the 

 destruction of the Polypide, as is found to be the case with other Polyzoa in the oldest part 

 of the polyzoarium. 



Concluding Remarks. 



It will be seen from the foregoing description that the Genus Rhabdopleura differs 

 in nearly all essential points from the ordinary Polyzoa', far more than Allman seems to have 

 conceived. If we compare what is here communicated with the chief points which have been 



