HOMOLOGIES. 231 
onous, notwithstanding its absolute permanence. 
In short, drop off the stem of the Crinoid, and 
depress its calyx to form a flat disk, and we have 
an Ophiuran ; expand that disk, and let it merge 
gradually in the arms, and we have a Star-Fish ; 
draw up the rays of the Star-Fish, and unite 
them at the tips so as to form a spherical outline, 
and we have a Sea-Urchin ; stretch out the Sea- 
Urchin to form a cylinder, and we have a Holo- 
thurian. 
And now let me ask, —Is it my ingenuity that 
has imposed upon these structures the conclusions 
I have drawn from them ?— have I so combined 
them in my thought that they have become to 
me a plastic form, out of which I draw a Crinoid, 
an Ophiuran, a Star-Fish, a Sea-Urchin, or a 
Holothurian at will? or is this structural idea 
inherent in them all, so that every observer who 
has a true insight into their organization must 
find it written there ? Had our scientific results 
anything to do with our inventive faculties, every 
naturalist’s conclusions would be colored by his 
individual opinions ; but when we find all zodlo- 
gists converging more and more towards each 
other, arriving, as their knowledge increases, at 
exactly the same views, then we must believe 
that these structures are the Creative Ideas in 
living reality. In other words, so far as there is 
truth in them, our systems are what they are, 
