12 SYNOPTIC KEY 



4(1) Polyps solitary or colonial, large, medusa always 

 absent; marine; the sea anemones, corals, etc. (Pratt, 

 132.) Class Anthozoa 



Class HYDROZOA 



1(10) Hydroid form present, frequently prominent, mostly 

 marine but with some fresh-water forms. 2 



2(3) Almost always fresh-water animals; polyps solitary, 

 without medusa forms or medusa-like buds. (Pratt, 

 92; W. and W., 320.) Order Hydrariae 



3(2) Usually marine forms (rare in fresh water). 4 



4(5) Colonies with a coral-like skeleton surrounding the 

 bases of the branching polyp forms. Medusa buds 

 usually remaining attached to the colony. (Pratt, 93.) 



Order Hydrocorallinae 



5(4) Colonies without a coral-like skeleton. 6 



6(7) Colony free swimming, containing a large number of 

 individuals of different kinds usually supported by an 

 air-bladder float. Portuguese man-of-war. (Pratt, 

 121.) Order Siphonophora 



7(6) Colony not free swimming although they may give 

 off free-swimming medusae. 8 



8(9) Without protective cup (hydro theca) about the 

 hydranth, or (gonangium) about the medusa buds; 

 medusae with gonads on the manubrium and when set 

 free with photoreceptors and lacking lithocysts. (Pratt, 

 94.) Order Tubulariae (Anthomedusae) 



9(8) With a hydrotheca and gonangium; medusae with 

 gonads on the radial canals and when set free with 

 lithocysts but lacking photoreceptors. (Pratt, 104.) 



Order Campanulariae (Leptomedusae) 



10(1) Hydroid form lacking (or minute if present). 11 



