CYDIPPE, 131 



a number of free-swimming forms, called Ephyrce, An Ephyra has 

 eight long arms, per-radial and ititer-radial^ down which are produced 

 the eight primary canals. The end of each arm is bifid, forming the 

 two lappets, between which is the tentaculocyst. By differential growth 

 the Ephyra fills up the ad-radial depressions and becomes a young 

 Aurelia. The tseniolse disappear, leaving only the gastric filaments, 

 whilst the bases of the septal fimrtels form the sub-genital pits. 



Here we have a metagenesis, as in Obelia, but the scyphula does not 

 form a true colony, abbreviating this stage by rapid transverse fission. 



Cydippe is one oi the most beautiful little organisms to be found in 

 the sea. It is pelagic and appears like an almost spherical transparent 

 ball of glass, usually about one-half inch in diameter. It feeds 

 voraciously on pelagic organism.s, e.g. , young fish. When alive it moves 



Fig. 65. — Cydippe Plumosa. 



(After Chun.) 



Tentacle with 



Adhesive Cell 



Row of Combs, 



Longitudinal Canal. 



with ceaseless activity and is iridescent with rainbow (interference) 

 colours. One axis is slightly longer than the other, at one end of which 

 (oral) is the mouth ; at the aboral end is a sense-organ. From oral 

 to aboral end there run eight meridional rows of rapidly moving combs 

 which are formed by a row of cilia fused at their base. All the combs 

 strike in an oral-aboral direction and the result is a steady, fairly rapid 

 movement forward. Two long tentacles trail behind the animal and 

 give stability to its movements. They bear small branches which are 

 covered with spirally stalked adhesive cells. The tentacles are very 

 sensitive and can be completely retracted within a pair of sheaths 

 or pockets. The mouth leads into an ectodermal gullet which 

 passes into a stomach. The stomach tapers towards the aboral 

 end and branches into four ducts which open symmetrically round 

 the aboral sense-organ. 



