234 THE EVOLUTION OF THE METAZOA 



is placed at the beginning and that of Rhizostomae at the 

 end of the system; the second generally prevalent characteris- 

 tic of this system is that Lucernariidea are followed by Carybde- 

 idea (also called Cubomedusae), and Rhizostomae by Semae- 

 ostomata. The fifth order Coronata is placed in the middle 

 (this is the sequence in Krumbach's Handbuch derZoologie). Fre- 

 quently, we find three orders only mentioned (e.g. by Claus), 

 and the two orders Semaeostomata and Rhizostomae united 

 in one order (as Discomedusae or Discophora), and the first 

 two orders grouped together as Calycozoa, etc. 



It is clear already now that Lucernariidea cannot be placed at 

 the basis of the system of Scyphozoa, even if they give the 

 impression of being more primitive forms. It is completely 

 impossible that scyphomedusae had developed from scypho- 

 polyps during their sessile way of life, as was formerly 

 believed by Goette in connection with hydromedusae. Taking 

 into consideration the well -founded supposition that the polyp 

 is the primary form, we must consider it as possible that the 

 broadened oral half had been separated by means of a trans- 

 verse division from the aboral half of the polyp which con- 

 tinued to live as a sessile animal. This oral half had simultane- 

 ously taken over the gonads and was transformed into a 

 medusa. We must therefore explain the mixture of charac- 

 teristic properties of the polypoid and medusoid forms that can 

 be observed in Lucernariidea, and that has been correctly 

 emphasized by numerous specialists (especially by Krumbach 

 and by Tochru Uchida, 1929) as being due to the fact that 

 the separation of the medusoid half had been secondarily 

 discontinued (we will meet something similar in Hydrozoa), 

 and that since then the medusoid form has become weU 

 enough adjusted to the life in the benthos so that finally 

 something new has been developed as a result of this amalga- 

 mation. The transverse division (not the budding) which takes 

 place but once, seems also to be a primary event; it can be 

 repeated after the passage of an interval of time; this can lead 

 finally to a quick series of multiple transverse divisions, a 



