184 Transactions of the Royal Microscopical Society. 
error, for I treated the disk as continuous all round the sinus ; and 
if, as Mr. Davis suggests in his paper, development from some 
other form is to be accepted as the mode in which Conochilus 
attained its present appearance, then I should offer the following 
suggestion, namely, that in endeavouring to arrange its disk to the 
best advantage for picking up trifles in a crowd of fellow-creatures 
grouped in a spherical form, it found it necessary to arrange the 
collecting cilia round the sinus ; and to do this, it tilted the disk 
and brought the lower points of the ciliary lobes like a collar for- 
ward and round its neck — ^just as if a sailor were to cut a large 
slit in his tarpaulin hat behind, at the lower edge, and then draw 
the two cut corners round his neck, so as nearly to meet under his 
chin, and keeping the hat on the back of his head, proceed to turn 
his face upwards (see Fig. 13). The incision under the calcars 
suggests where these two points of the disk may have come from. 
At the same time, and though I know that I am in a small 
minority, yet I confess I cannot see how evolution helps us in the 
least with such an animal ; because the moment you suggest a 
previous form, you ask. Where is it ? and I should not like to 
point to any rotifer sufficiently near Conochilus to justify one in 
looking upon it as a predecessor in title. To me, the whole rotifer 
world, in fact, is a wild collection of puzzling forms. There is 
plenty of likeness and mixture, but there are no links that I can 
see. There are many forms that make you think of another, but 
which, when closely examined, range away widely from it in some 
important particular. To me, the rotifers have, in fact, ever been, 
and are, a stumbling-block in the way of accepting the development 
theory as the complete and vast agency that so many now consider 
it, and the manducatory organs seem to me to deserve close 
consideration in connection with the subject. If anywhere, I 
should have expected to find in the rotifer world confirmation 
strong of the theory — gradations and links in perfect order — 
classification easy and systematic ; instead of which there would 
seem to be some other principle at work there which runs 
quite athwart any notion of regularity, which baffles every scheme 
of classification, and exhibits most unexpected complications — 
striking gaps where we are led to expect continuity. I cannot 
help anticipating that the time may come when these very same 
gaps, existing as they do throughout the animal kingdom, will be 
recognized by scientific observers exactly as the irregularities of 
Uranus were fixed upon by Adams and Leverrier, and accepted as 
indicating another and an outer force. As long as this view is 
overlooked, so long will science be retarded ; for what we forget 
we fail to seek for ; and we are apt to stop gaps with great names. 
We want a principle in direct relation to these regularly recurring 
hiati—Q. principle which, accepting the fact that the disappearance 
