156 THE EVOLUTION OF THE METAZOA 



Even the word "medusoid" does not seem to be suitable 

 here, it should continue to be used in connection with the 

 anthocyathus, if it is necessary at all to have a special name 

 in this case. The luxuriously developed inner calcareous 

 skeleton had probably been a very important factor of the 

 case of Fiitjgia. With regard to the life cycle, there exists a 

 deep chasm between the recent Anthozoa and Scyphozoa. 

 A closer union of these two classes into one of Anthozoa, 

 a suggestion which goes back to Goette, is a mistake which 

 has fortunately now been completely rejected. In the Scyp- 

 hozoa a special freely swimming generation has been developed 

 by way of the transverse division which they had inherited 

 from their anthozoan ancestors and because of the absence 

 of a heavy inner calcareous skeleton. This generation, i.e. the 

 Scyphomedusae, have taken over the sexual function and 

 later it has assumed the leading role. In this w^ay metagenesis 

 becomes even more clearly perceptible. To the primary polyp 

 form (it is now called a scyphopolyp in opposition to the 

 anthopolyp) w^hich reproduces only asexually has been given 

 a special name, i.e. a scyphistoma or a scyphostoma, and this 

 again has been a reason for unnecessary misunderstandings. 

 Scholars have frequently tried to represent the polyp generation 

 of Scyphozoa as a purely juvenile form, and thus to degrade 

 it to a larva. They have referred in this connection to a com- 

 pletely special and abnormal case which occurs under special 

 circumstances, i.e. w^hen a scyphopolyp transmutes in toto into 

 a scyphomedusa, or an ephyra (i.e. a medusan larva), instead 

 of developing a "medusan larva" by way of transverse division 

 (strobilation). 



Fortunately enough, there have survived many species of 

 Scyphozoa that have preserved conditions that were formerly 

 typical of them. Nausithoe punctata is one such species which 

 has already been mentioned. Its polyp generation produces 

 irregularly formed cormi (colonies) wdth a rich development 

 of the "periderm." Though gonocytes still continue to be 

 produced in the basal part of the polyps, they migrate now 



