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Zoology. — "(>)) tJic rchitiiDishij) of raridiis inri'iicJiratc phi/hi.''' 



]U- Pl-Of. A. A. W. llL-URKCHT. 



Ill an elaborate paper entitled "Beitrage zii einer Trophocöltlieorie," 

 pnblished in 1903 in the 38tli volume of the "Jenaische Zeitsclirift 

 fill- A'atnr\vis8en.schaft," Prof. Arnold Lang of Ziirich (p. 68— 77) 

 gives a clear exposition of what has been, in his opinion, the phy- 

 logenesis of the Annelids. 



In this pedigree he places, beginning with a protocoelenterate, 

 a cteno[)liore-like being, a plathelminlh, an intermediate form resem- 

 bling a triclade, an animal in the shape of a leech which already 

 possesses metameric segmentation and Itnally a })roto-annelid. 



The grounds on which he bases this phylogenesis, compel us to 

 acknowledge important relations between these animal groups. But 

 whether this kinship testities to a descent in the order given bj' Lang, 

 or whether the order has for the greater part been a rcA'ersed one, 

 deserves to be examined more closely. 



In my opinion there Ctenophores should not be placed at the 

 beginning of the series, nor are they to be considered as links between 

 Coelenterates and worms, but they have to be looked upon as animals, 

 which form the last offshoots of an evolutionary series, leading from 

 the Annelids via the Hirudinia and the Plathelminthes. Of these 

 latter there have been some which gradually assumed a pelagic 

 mode of life and have become Ctenophora, the external resem- 

 blance of which with transparent jelly-fish seemed l(j justify their 

 being placed l)y the side of the Coelenterates. 



Let ns first test the grounds on which that combination has until 

 now^ been defended (see e. g. G. C. Bourne in Ray Lankkster's 

 Treatise on Zoology, 1900). 



The presence of a gastro- vascular system and the absence of an 

 independent coelom, as well as the presence of a subepithelial 

 jierveplexus are characteristics which can be found not only with 

 the Coelenterates, but also to a great extent with the Plathel- 

 minths. 



The tentacles of the Ctenophores ha\'e quite wrongly been compared 

 to those of the medusae, while the analogy of the adhesive cells 

 of the CUenophora with the nematocysts of the Cnidaria is also 

 defective. And if nematocysts should I)e found in some Ctenophora, 

 no conclusions should be based on this, because they also occur in 

 Molluscs, Plathelminths and Nemertines. 



The absence of nephridia, the general stnu-lural proportions and 

 the gelatinous composition of [>art of the organism are details which 



