466 Pleasant Ways in Science. 



diversity of appearance presented by the same animal at dif- 

 ferent stages of its existence. In the insect world we know 

 the caterpillar, the chrysalis., and the butterfly. The young 

 Cyclops, a well-known water flea, common in all ponds, and 

 with which our microscopic readers must be well acquainted, 

 differs greatly from the adult form in the shape of the body, 

 the absence of the long tail, the want of antennas, and many 

 other particulars. Still more remarkable are the differences 

 between the young crab, in shape like a helmet with a tail to 

 it, and the adult individual, and between the young star-fish, 

 beginning life like a painter's easel, and the full-grown form. 



What constitutes the individual identity of creatures that 

 have no continuous consciousness, or no consciousness at all, 

 and which in their separate stages differ as much as if each 

 stage constituted the existence of a distinct being ? At one 

 time it was thought by some philosophers that all the organs 

 and apparatus developed in subsequent life-stages existed in 

 the first stage in a rudimentary form. This notion is un- 

 tenable. The egg- stage of animals, widely differing from each 

 other, may be indistinguishable, and yet in each egg some 

 special arrangement of forces and materials exists which deter- 

 mines the kind of development that shall ensue ; and in animals 

 that pass through many changes of form and aspect, the form 

 that precedes is, in effect, the parent of that which is to follow. 



Are we to regard the seed and the plant as belonging to one 

 individual identity. We cannot do otherwise ; and in this case 

 we have to note that from the seed the infant plant really 

 grows, and the adult plant grows from the infant germ. The 

 entire plant, at any one time, is continuous in its structure. 

 But there are differences between buds and eggs, and must we 

 take all the beings that arise from animal or vegetable buds 

 of the same individual as partaking of its individuality ? A 

 bud may be, for example, a portion of an individual plant, and 

 may be developed into a similar plant — aphides or plant-lice 

 produce numerous offspring by buds as well as others at certain 

 periods by eggs. Such cases are rather multiplications of the 

 individual, than the production of fresh individuals. 



We are accustomed to regard an animal as something 

 complete in itself; but what shall we say when an organ of 

 reproduction moves about as a separate thing from the creature 

 of which it is a dissociated part ? Natural history presents 

 these curious problems. Facts of this kind have appeared, 

 and more will appear from time to time, in our pages. They 

 suggest profound and interesting thoughts. In this paper we 

 have only approached the threshold of great questions. We have 

 skimmed over a wide surface, hoping rather to stimulate inquiry 

 in many directions than endeavouring to satisfy it in any one. 



