150 AFFINITIES AND GEOGRAPHICAL 



forms of the mature organisms ; another is to examine the 

 embryotic progress, and watch the succession of forms there 

 presented. It has for some time been ascertained that no 

 animal, in the course of its development, passes through the 

 forms of all the animals meaner than itself. For example, the 

 sea-nettle is at one time like the monad, an infusory animal- 

 cule, and then like the polyp; the mollusk is successively 

 like the monad and polyp, but never like the sea-nettle. The 

 articulate animal, again, is never like the polyp or sea-nettle, 

 but proceeds at once from the monad form to that of the 

 worm. This Professor Owen calls being " obedient to the 

 law of unity of organization only in its monad stage." ( 7l ) The 

 fact has been held as a difficulty in the way of the doctrine of 

 unity ; but perhaps it is only one of the same nature with 

 that intimated regarding the assumed scale of being. I see 

 animals classed by their affinities in distinct lines, or series, 

 which I regard as stirpes or races. I would therefore expect 

 the unity of organization to be liable to some such limitation 

 as Mr. Owen points out. Is it not, in reality, that each stirps 

 has a unity of organization for itself, or, in other words, that 

 there is such a unity only as far as each particular series of 

 animals is concerned ? These breaks in unity and the breaks 

 in the chain of being are but one thing : they are only dis- 

 turbances to our preconceived ideas, not to a true view of 

 nature drawn from its realities. 



I shall not attempt to place all these obscure animals in 

 genealogical series. The state of zoological science demands 

 that such an effort should be postponed for several years to 

 come. Let us limit our attention to one class, the Echino- 

 dermata, or star-fishes, which are perhaps improperly ranked 

 with other Radiata, seeing that their character is so much 

 superior. In general highly organized, and enjoying free 

 movement at the bottom of the sea, these animals are signally 

 destructive. Admitted to be in their lower forms intimately 

 allied to the Polyps, they probably start in some portion of 

 that extensive order. In their own class, however, as far as 

 traceable backwards, they commence with the encrinus or 

 stone-lily, a group of animals of which we have seen many 



