ITS DEVELOPMENT. 219 



The animalcule settled down upon the smooth sur- 

 face, but did not immediately affix itself, for it re- 

 mained here gyrating on its axis, yet without leaving 

 the spot which it had selected, in the closest prox- 

 imity to the leaf. At length, perhaps after an hour's 

 play, its rotation became momentarily interrupted, 

 and resumed with intervals of longer and longer dur- 

 ation, until at length it moved no more. The little 

 gemmule was permanently adherent. 



Imagine the tiny, helpless atom of unresisting flesh, 

 now become immovably fixed to this exposed surface. 

 It has relinquished the only defence it possessed 

 against violence, that of swiftness. Its first need is 

 protection ; and, Kobinson-Crusoe-like, it immediately 

 sets about building a fortress. Nor is it, helpless as 

 it seems, at all destitute of resources ; for, from the 

 whole surface of its soft body, ere now bristling with 

 cilia, a secretion is poured out, which, speedily hard- 

 ening, setting under water like the Aberthaw lime, 

 acquires a firm horny consistence, of considerable 

 elasticity, and perfect translucency. The softer parts, 

 which have hitherto presented a homogeneous sub- 

 stance without distinction of organs, now separate 

 themselves from the inner walls of the horny coat, 

 which thus becomes an enclosing case or cell ; while 

 the flesh develops distinct and ' well-defined organs, 

 such as a crown of ciliated gill-threads around a 

 mouth, a long gullet leading to a stomach, an intes- 

 tinal canal opening by a cloacal orifice, and many 

 threads and bands of muscular tissue, by means of 



