In this case the only regularity to be noted is the rectangularity of the completed surface. There are but few of the inner figures bordered by four adjacent ones. The direct environment of the frog consists of two figures; the guitar is hemmed in by three, the cock by five and the ostrich (if that is what it really is) by six. The sum total can only be arrived by careful counting.

It's of interest to us that only one figure is not a creature of some sort. In our reading we haven't been able to find any stated meaning to the guitar, but Escher did almost everything with a purpose.

Escher occasionally worked on irregular filling of plane surfaces such as this print Mosaic II. He said they could never have been produced without years of training in regular surface-filling and the only reason for their existence is one's enjoyment of this difficult game.