put away your fish and go home; perhaps you will be ready with a better
answer in the morning. I will examine you before you look at the fish.'

This was disconcerting. Not only must I think of my fish all night,
studying, without the object before me, what this unknown but most
visible feature might be; but also, without reviewing my new discoveries,
I must give an exact account of them the next day. I had a bad memory;
so I walked home by Charles River in a distracted state, with my two
perplexities.

The cordial greeting from the Professor the next morning was
reassuring; here was a man who seemed to be quite as anxious as I that
I should see for myself what he saw.

'Do you perhaps mean,' I asked, 'that the fish has symmetrical sides
with paired organs?'

His thoroughly pleased 'Of course! of course!' repaid the wakeful
hours of the previous night. After he had discoursed most happily and
enthusiastically--as he always did-upon the importance of this point,
I ventured to ask what I should do next.

'Oh, look at your fish!' he said, and left me again to my own devices.
In a little more than an hour he returned, and heard my new catalogue.

'That is good, that is good!' he repeated; 'but that is not all; go
on;' and so for three long days he placed that fish before my eyes,
forbidding me to look at anything else, or to use any artificial aid.
'Look, look, look,' was his repeated injunction.