120 



INVEBTEBBATM MOBPHOLOOT. 



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 Coelentera, but at the same time 

 depart so widely in structural and histological characters 

 from the Cnidaria and Porifera that it seems advisable, 

 until further evidence is forthcoming, to consider them as a 

 group apart. 



All the Ctenophores are pelagic and are of great transpa- 

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



mc 



Pig. 66. — BoUna hydatina (after Cmra). 

 cp = ciliated plates. tc = funnel-canal. 



g = stomach or funnel. 



I = lobe. 



mc = stomodseal canal. 



In form they vary greatly, some being almost spherical or 

 pyriform {Pleurohrachia), sometimes with broad lobes project- 

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



