BRITISH ZOOPHYTES. 209 



they can be serviceable for this purpose, and as in no 

 case can they transfer any captured food to the mouth, 

 they are probably defensive in their functions, and by 

 their appearance and movem'ents ward off intrudei'S 

 from the colony. 



The vibraculum is a long movable bristle which 

 probably serves a similar purpose to that of the avicu- 

 larium, as it is generally placed where it can move 

 backwards and forwards before the orifice of the 

 zooecium. 



Reproduction in the Polyzoa is of two kinds — 

 asexual, for the development of the colony, and sexual. 

 In the latter case the ova, which are contained in the 

 ovary, are fertilized by the spermatozoa, and develop 

 in the body cavity into free ciliated larvas often beauti- 

 fully coloured. In many species the ova after fertili- 

 zation are conveyed to an ovicel or ooecium which is 

 developed by budding from the zooecium, with which 

 it is in direct communication, and which serves, 

 according to Professor Huxley, for a marsupial cham- 

 ber. These ovicels are often very prominent and 

 attractively sculptured parts of the colony. Where 

 the reproduction is asexual, that is by gemmation or 

 budding, the buds, as before stated, are developed 

 from the eudosarc. 



Amongst the fresh-water Polyzoa there is a curious 

 method of reproduction by statoblasts or " winter 

 eggs," which are spherical bodies covered with net- 

 work, and sometimes armed with spines round the 

 circumference. They are regarded as free buds or 

 stationary germs, and not as ova. They are not 

 hatched in the colony, and are evidently intended as 

 " reserves of generative force,'^ to preserve the repro- 



p 



