TIMA FORMOSA L. Agassiz 



Material. Tima formosa is not uncommon in the North 

 Atlantic. Along the New England coast the mature medusae are 

 found in March, April and May and disappear before June. 

 North of Cape Cod they are found in autumn and winter. The 

 specimens should be preserved in formalin. For microscopic 

 study a specimen must be preserved in i% osmic acid. 



Descriptive Part 



Tima formosa belongs to the class Hydrozoa and has a life- 

 cycle with complete metagenesis. The hydrosome has been bred 

 from a fertilized egg by Agassiz, but is very little known, quite 

 insufficiently in fact, to recognize it in nature. The medusome is 

 one of the largest American hydromedusas. 



The edge of the medusa is a perfect circle and the body, which 

 is called the umbrella may be best likened to a bell. The outer 

 surface of the bell is called the exumbretta, the inner surface the 

 subumbrella. The exumbrella has the shape of a paraboloid and 

 its axis is somewhat longer than the radius of the base. Owing 

 to the thickness of the bell at its apex the axis of the subumbrella 

 is considerably shorter. Moreover, the subumbrella has a 

 peculiar shape inasmuch as its median portion hangs down 

 through the opening of the bell, in the shape of a cone called the 

 peduncle. At the end of the peduncle is a short manubrium with 

 a mouth-opening surrounded by four long lips with transverse 

 folds. The mouth leads into the quadrangular cavity of the 

 manubrium, which is called the stomach. Four radial canals 

 arise from the corners of the stomach and run at even distances 

 from each other in the wall of the peduncle toward its base, bend 



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