14 



MARINE ANIINIALS OF MASSACHUSETTS BAY. 



jelly-fish, the Cyanese, though one is at a loss to imagine what 

 sustenance they can derive from animals having so little solidity, 

 and consisting so largely of water. 



Fig. 11. 

 Fig. 13. 



Arachnactis. (AracJmactis brachiolata A. Ag.) 



Among the nomadic Polyps is a small 

 floating Actinia, called Arachnactis, 

 (Fig. 11,) from its resemblance to a 

 spider. They are found in great plenty 

 floating about during the night, feeling 

 their way in every direction by means 

 of their tentacles, which are large 

 in proportion to the size of the animal, 

 few in number, and turned downward 

 when in their natural attitude. The 

 partitions and the digestive cavity en- 

 closed between them are short, as will 

 be seen in Fig. 11, when compared to 

 the general cavity of the body floating 

 balloon-like above them. Around the 

 mouth is a second row of shorter ten- 

 tacles, better seen in a younger speci- 

 men (Fig. 12). This Actinia difiers 

 from those described above, in having 

 two of the sides flattened, instead of 

 being perfectly circular. Looked at 

 from above (as in Fig. 13) this differ- 

 ence in the diameters is very percepti- 

 ble ; there is an evident tendency to- 

 wards establishing a longitudinal axis. 

 In the sea-anemone, this disposition is 

 only hinted at in the slightly pointed 

 folds or projections on opposite sides of 

 the circle formed by the mouth, which 

 in the Arachnactis are so elongated as 

 to produce a somewhat narrow slit (see 



Arachnactis bracliiolata A. Ag., greatly magnified. Fig. 12. Young Arachnactis. 



Toung Arachnactis seen so as to show the mouth. 



Fig. 12. 



