(W 



62 



FACTS AND FANCIES. 



scribing this animal he takes pains to inform us 

 that it is more different from an ordinary fish 

 than £. fish is from a man. Yet, as he illustrates 

 its curious and unique structure, before we are 

 aware, the lancelet is gone and a fish is in its 

 place, and this fish with the potency to become 

 a man in due time. Thus a creature interme- 

 diate in some respects between fishes and mol- 

 liisks, or between fishes and worms, but so far 

 apart from either that it seems but to mark the 

 width of the gap between them, becomes an 

 easy stepping-stone from one to the other. 



In like manner, the ascidians, or sea-squirts — 

 mollusks of low grade, or, as Haeckel prefers 

 to regard them, allied to worms — are most re- 

 mote in almost every respect from the verte- 

 brates. But in the young state of some of 

 these creatures, and in the adult condition of 

 one animal referred to this group {Appendic- 

 ularia), they have a sort of swimming tail, 

 which is stiffened by a rod of cartilage to en- 

 able it to perform its function, and which for a 

 time gives them a certain resemblance to the 

 lancelet or to embryo fishes ; and this usually 

 temporary contrivance — curious as an imitative 

 adaptation, but of no other significance — be- 

 comes, by the art of " appearing and disappear- 



