THE LAW OF LIKEXESS, AND ITS WORKIXG. 213 



mately, however, they develop eggs, and with the production 

 of the eggs the clear, elegant, glassy bodies undergo disso- 

 lution, and vanish away amid the waters, to which, in the 

 delicacy of their structure, they presented so close a resem- 

 blance. From each egg of the jelly-fish bud there is gradu- 

 ally developed, not a medusa, but a zoophyte. The egg, in 

 in fact, develops a single bud of the zoophyte, and this 

 primitive bud, by a process of continuous budding, at last 

 produces the connected tree-like form with which the life- 

 history began. Thus the zoophyte is seen to give origin to 

 a jelly-fish, and the jelly-fish in turn reproduces the form of 

 the zoophyte, one generation of animals, as the older na- 

 turalists believed, " alternating " in this way with another. 



The law of likeness would at first sight seem to be ill 

 adapted, in virtue of its essential nature, to explain the cause 

 of an animal, such as the zoophyte, producing an entirely 

 different being, represented in the present instance by the 

 jelly-fish bud; and it might appear to be equally inexplicable 

 that the progeny of the jelly-fish should revert to the zoophyte- 

 stock and likeness. The case of those curious oceanic 

 organisms, allied to the " sea-squirts," and known as salpae, 

 presented to the zoologist of former years phenomena of an 

 equally abstruse kind. The salpae are met with floating on 

 the surface of the ocean in two distinct forms. One form 

 exists in the shape of a long connected " chain " (Fig. 30) of 



FIG. 30. Part of a chain of salpae. 



individuals, whilst the other form is represented by single 

 salpae (Fig. 31). It was, however, ascertained that these two 

 varieties were linked together in a singularly intimate manner 

 by their development. The chain-salpse were found to 



