226 REPRODUCTION OP PLANTS AND ANIMALS. 



in floating sea-weed, and very frequently accompanied 

 by the beautiful lanthina, or " Blue Snail-shell," a 

 singular Mollusc that equally "swims on bladders." 

 In the Velella of our shores the sail is immovable, 

 and the vessel is therefore much at the mercy of the 

 winds, but there is an exotic species which is said to 

 have the power, by the contraction of muscular bauds, 

 to lower its sail at pleasure. 



Many circumstances in the history of the ACALEPH.E 

 are calculated to excite curiosity or admiration, but, 

 perhaps, there is no fact connected with them more 

 wonderful than the mode of their reproduction from 

 gemmae or buds. It is a character of the vegetable 

 kingdom that its organisms propagate themselves in 

 two ways : one by seeds, formed by special organs 

 called flowers ; the other by gemmae or buds, which 

 may be developed from any part of the cellular sub- 

 stance of the plant. Both modes of reproduction 

 effect a similar object the continuance of the species : 

 but it is observable that individual characters are 

 more strictly perpetuated when plants are multiplied 

 by buds than when they are grown from seeds ; hence, 

 one mode of growth is said to be a multiplication of 

 the individual plant, the other, a propagation of the 

 species through new individuals. In the higher classes 

 of animals propagation by gemmae does not occur : the 

 young are brought forth either in a fully-formed state, 

 or in eggs, from which they will in time be hatched. As 

 we descend lower in the series we find the process con- 

 siderably varied, and become familiarized with certain 

 transformations through -which the young creature 



