SEA-MA T MAKERS. 3077 



transition- forms link the two together. The setae- 

 are sometimes of enormous size, and of great strength, 

 and in certain species assume a locomotive function 

 acting probably as oars, and propelling the colony 

 which in that particular group are free in the adult 

 state. This justifies the remark that " in the history 

 of these appendages we have a curious illustration: 

 of the variety of function that may connect itself 

 With the same morphological element." 



Reproduction is secured in these Polyzoa by two 

 methods, by regular sexual elements, and by the 

 asexual method of budding, or gemmation. The 

 majority of species are monaecious, male and female 

 organs being present in each cell, but some species 

 are unisexual, either wholly male or wholly female, 

 A contractile cord, called the funiculus, is attached 

 to the bottom of the stomach, and passes down to the 

 bottom of the cell. It is considered an established fact 

 that the male elements are derived universally from 

 this funiculus, and in a great number of species the 

 ova are also developed in the funiculus, sometimes 

 apart from this organ, and sometimes attached to the 

 cell-wall. It is still a question whether the ova are 

 fertilised by male elements, developed in the same 

 cell, or whether by those liberated from other cells. 

 Their dispersion in immense numbers into the sur- 

 rounding water seems to indicate the latter conclu- 

 sion, and it is not improbable that in different 



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