( 840 ) 



by no iiieaiis interfere witli ;i view which wouhl see in the Cteno- 

 phora Plathehnintlis that ha\ e heeonie [)elagie. 



Tiiat the connectioii whieh Hakckkl intended to establish between 

 Coelenterates and Ctenojihora, when describing' Ctenaria ctenophora, 

 is an imaginary one, has ab-eady repeatedly been sho^^'n, so e. g. 

 by R. Hertwig ("Jen. Zeitschr". lUI. 14, p. 444), G. ('. Bourne 

 (1. c. \). 445) and others. The lirst-niejitioned author says emphati- 

 cally (1. c. p. 445): "Die (Henophoren sind Organismen welche sich 

 von den iibrigen Coelenteralen sehr weit entfernen." Also Korschelt 

 and Heider in their excellent handbook on the embryology of the 

 invertebrates are inclined ([). 100) to look upon the Ctenophora rather 

 as an independent branch of the animal Ivingdom, the comiection of 

 which with that of the Coelenterates lies far backward. On the other 

 hand they point out unmistakable relations between the phylogenesis 

 of the (Henophora and that of the l»ilateria (Annelids, Arthropoda, 

 Molluscs etc.). They expressly a<ld that the side-hrauch of the animal 

 kingdom on which the (Uenoi»h(ira are ])laced ciiiinot he consijh'n'd 

 Its luiriiKj fin-ii'ishcd <i sl({vtuuf-[HHni foi' liujlwr <intiii<il fonn.s. 



Ctenojdana and ('oeloplana are consequently not considered by 

 them as advancing steps of development in the <lirection of the Plat- 

 helminths, but as aberrant, creeping CteJiO[>hora. L.VNCr himself has 

 ackno\>ledged on page 72 of his great handboolv that the place 

 of the Ctenophora among the other Cnidaria is a very problematical 

 one and that their eml)ryologT distingnishes them from all ('nidaria. 



So there can be no douitt, considering all this, that the tie 

 which nowadays keeps together the Ctenophora with the Coelente- 

 rates has of late years been considerably slackened. ( hie etfort and 

 it may be entirely removed ^). 



What on the othei' hand have we to think about possil)le relations 

 between Ctenophora and Plathelminths? These relatiojis appear es[»e- 

 cially striking to those who have occupied them.sehes with the 

 endnyological development of both classes. 



Thus SElenka has already in 1881 summarized this analogy under 

 twelve heads (znr Entwickelungsgeschichte der Seeplanarien, S. 283). 

 Also Lang in his monograph on Polyclads (1884) has em])hatically 

 pleaded for that relationship, although in a separate paragraph he 

 acknowledges the existence of real difliculties. Also in his most recent 

 paper he adheres to the same opinion. 



The discovery of two very peculiar genera of animals has still more 



1) A paper, published very recently in tlie Zoologische Anzeiger (IJtl. 27, p. 2:2 )) 

 on a new, much simplified Ctenophore, does not, as its author Dawydoff sug- 

 ^'ests, strengthen the bond between Coelenterates and Ctenophora. 



