ZOOPHYTES OF GUERNSEY. 167 



single individual, and the stomachs of the several polyps are 

 connected by tubes, and communicate with the cavity of the 

 central stem. It is clear, therefore, that any food taken in 

 bv one polyp would be shared by the other members of the 

 colony ; so that in fact the entire polypary would form, as it 

 were, only a single individual with many mouths. And the 

 number of individuals forming a colony is sometimes prodi- 

 gious. Dana describes an East Indian species of Afjlaojjlieida 

 which attains a height of three feet, and he computes that the 

 number of polyps on a single specimen is not less than eig^ht 

 millions, all the offspring of a single germ, and produced by 

 single buddings. Instead of being naked, like the Freshwater 

 Hydra, most of the marine species belonging to this section 

 secrete a horny or calcareous polypary which protects the soft 

 connecting tissue, and forms receptacles in which the separate 

 polyps are lodged. 



The extraordinary phases of reproduction in the Hy- 

 droida present some of tlie most curious life-histories known 

 to science. Besides the ordinary polypite, or alimentary 

 zooid, which resembles the Hydra, there are produced at 

 certain seasons of the year other buds of a totally different 

 form, called goiwjjhorea^ or reproductive zooids. Within these 

 are developed small medusa-like bells, which on arriving at 

 maturity escape, and propel themselves through the water by 

 rhythmical contractions, just like the large jelly-fishes. After 

 a period of active existence these beautiful miscroscopic bells 

 sink to the bottom and produce other reproductive forms like 

 ciliated larv^, which move about for a time, and then attach 

 themselves ; after which, by giving forth buds, they ultimately 

 produce the maturely-developed Hydroid. And so the 

 wonderful cycle of evolution goes on. 



It is not surprising that for a long time these free- 

 swimming forms were regarded by naturalists as entirely 

 distinct animals, until the life-cycle of a number of them had 

 been carefully traced. No result of microscopical research 

 created more surprise than the discovery of the close relation- 

 ship which subsists between the Hydroid Zoophytes and the 

 Merlusoid Acalephic. The dissimilarity both in general aspect 

 and in mode of life between the immature form and the adult 

 polyp is so great that no one Avould ever imagine them to be 

 merely stages in the life of the same individual ; they differ 

 as widely as a caterpillar does from a butterfly. And so we 

 can perceive how appropriate, in a poetical, if not in a 

 scientific sense, is the old term Zoojjliyte, or animal-plant, 

 because the young free-swimming form is obviously an animal, 



