258 



ALTERNATE GENERATIONS. 



uniting all the Hydroid stems in its meshes, 

 and spreading over the whole surface on which 

 the colony has established itself. 



Hydractinia polyclina : a, sterile individual ; 6, fertile individual, producing 

 female Medusae ; d, c, female Medusae, containing advanced eggs ; /, $r, A, i, 

 cluster of female Medusae, with less advanced eggs ; o, peduncle of mouth, 

 with short globular tentacles ; c, individual with globular tentacles, upon 

 which no Medusae have appeared, or from which they have dropped. 



There is a very curious and beautiful animal, 

 or rather community of animals, closely allied 

 to the Hydractinia polyclina, which next de- 

 serves to be noticed. The Portuguese Man-of- 

 War so called from its bright-colored crest, 

 which makes it so conspicuous as it sails upon 

 the water, and the long and various streamers 

 that hang from its lower side is such a com- 

 munity of animals as I have just described, re- 

 versed in position, however, with the individuals 

 hanging down, and the base swollen and ex- 

 panded to make the air-bladder which forms its 



