120 



INVERTEBRATE MORPHOLOGY. 



CHAPTER VI. 



THE CTENOPHORA. 



THE group of forms known as the Ctenophora, to which 

 the systematic value of a class may be given, present no little 

 general resemblance to the Coalentera, but at the same time 

 depart so widely in structural and histological characters 

 from the Ciiidaria and Porifera that it seems advisable, 

 until further evidence is forthcoming, to consider them as a 

 group apart. 



All the Cteuophores are pelagic and are of great transpa- 

 rency and delicacy, due to the nature of the mesogloeal tissue. 



s 



tc 



FIG. 66. Bolina Jiydatina (after CHUN). 



cp = ciliated plates. tc = funnel-canal. 



g = stomach or funnel. 



I = lobe. 



me = stomodseal canal. 



In form they vary greatly, some being almost spherical or 

 pyriform (Pleurobrachia], sometimes with broad lobes project- 

 ing from near the oral extremity (Fig. 66, 1) (Bolina, Mnemi- 



