AURELIA AURITA (L.) varietas FLAVIDULA 

 Peron et Lesueur 



Material. Mature individuals of Aurelia flavidula may 

 be collected in summer and preserved in formalin. Scyphos- 

 tomae and strobilae are common on seaweed in October. Ephyrae 

 may be found in March and April. Material for microscopic 

 study should be fixed in i% osmic acid. The student should 

 study a mature medusa, a scyphostoma and a strobila preserved 

 in formalin, and the following prepared microscopic slides: a 

 cross-section through an arm of a mature medusa with embryos, 

 an ephyra stained in toto, a cross-section through a scyphos- 

 toma, a median longitudinal section through a scyphostoma. 



Descriptive Part 



Aurelia aurita is a typical representative of the Class 

 Scyphozoa. It is a cosmopolitan jelly-fish common in European 

 seas and the Atlantic and Pacific Oceans. The American variety 

 is known under the name of Aurelia flavidula. The life cycle 

 of Aurelia flavidula consists in an alternation of generations com- 

 bined with metamorphosis or development of the adult from a 

 larva. The whole life cycle is completed in one year and the 

 preponderance lies with the sexual stage or medusa, compared 

 with which the polyp is very small. The medusae begin spawning 

 toward the end of July. The eggs develop in small breeding 

 pouches of the mouth-arms of the female. Here they reach the 

 stage of a ciliated planula. The planulae leave their mother in 

 October and soon attach themselves to some seaweed or rocks. 

 The mouth appears and tentacles grow out around the peristome. 

 Thus a scyphopolyp or scyphostoma is formed. The scyphos- 

 toma begins to grow and produces by a peculiar method of 



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