NEW INTERPRETATION OF CNIDARIA 



263 



degree only, with the larvae of some Polycladida, among the 

 Turbellaria (Goette-Miiller's larva). 



It is hardly correct to use the word "larva" when we speak 

 about the planula. A planula is in reaUty only a sHghtly more 

 accentuated stage ot development which is unable to feed 



Fig. 46. Some examples of planktonic larvae of the Cnidaria. 

 A, longitudinal section of a planula with gastral cavity (Gonoihy- 

 rea sp., after Wulfert). B, a solid planula. C, actinula of Tubularia 

 sp. (after Hyman). D, later actinula of a narcomedusa (Pegantha 

 sp., after Bigelow.) E, cerinula of a ceriantthide larva {Arach- 

 «<2f//x dz/^/VdZ after Vanhoffen).F-G larvae of unknown zoantharians 

 Zoanthina sp. and Zoanthella sp. (after Senna). G, siphonula, a caly- 

 coforean larva (Galeolaria sp.) (after Metschnikoff). 



independently and which is therefore not fit to live long 

 in the real plankton. Its function, with a few exceptions, is 

 clearly to settle down not far from the place inhabited by its 

 "parents" and to develop into a new primary polyp. The 

 absence of an oral orifice and of an intestine which can be 



