PREVIOUS INTERPRETATIONS OF CNIDARIA 123 



in the two main forms of medusae (Scypho- and Hydromedu- 

 sae), and so there is no trace left of the primary internal 

 muscles. On the other hand, we can observe a strengthening; 

 of the longitudinal muscular tissue which lies under the skin 

 epithelium. This strengthening is appropriate to the function 

 these muscles have in certain areas, especially close to the 

 marginal tentacles, so that these muscles frequently show a 

 higher level of specialization and they become transversally 

 striped (e.g. according to Krasinska, in the subumbrella of 

 the trachyline hydromedusa Car marina hastata) ^ot they can even 

 appear as independent myoblasts (e.g. according to Krasinska, 

 in the subumbrella of the hydromedusa Neoturris). 



The opponents to the view that considers the polyp form 

 as primary in comparison to the medusoid form and which 

 sees in Anthopolyps the oldest form Cnidaria, should com- 

 pare the muscular conditions that can be found in Cnidaria 

 with those that can be found in other sessile animal 

 types; thus to compare those in Turbellaria with those in 

 Endoprocta (Camptozoa), those in Annelida with those in 

 Phoronidea and further with those in Ectoprocta, and finally 

 those in Branchiostoma with those in Tunicata. It is wrong to 

 require or to expect a progressive development in the general 

 muscle system of an animal body which adheres to the sessile 

 way of life, a supposition which one has to accept if one tries 

 to derive the Scypho- and Anthozoa from the Hydrozoa. 



The unique case of Stauromedusae, or better, say, Lucer- 

 nariidae is very interesting in this connection. These are not 

 simply medusae as they have frequently been depicted, but 

 real polypomedusae instead (Fig. 22). These Scyphozoa are 

 secondary solitary animals and they usually have readopted 

 the ability to move slowly over the sea bottom. At the same 

 time they have also abandoned the alternation of generations ; 

 their medusoid generation which was formed by way of trans- 

 verse division or strobilation is not severed any longer but 

 instead it remains with the polyp with which it forms a double 

 animal, a genuine polypomedusa, or a combination of a basal 



