SCIENCE IS MEASUREMENT 289 
a good series, proceeded to tabulate the measurements in 
millimetres. He was disappointed, however, not to find 
any such conformity to a general law as he had expected. 
It then occurred to him that in the larva change of form 
and increase of size are going on together, and that one 
organ might be diminishing relatively to another organ 
while it was increasing relatively to itself m a former 
stage. He therefore reduced his measurements to a 
common standard, expressing them in thousandth parts of 
the total length of the larva at each stage, and this usually 
enabled him to decide whether a given larva did or did 
not belong to a particular series. Apart from this, in one 
instance which he mentions his comparative measurements 
obtained a triumph parallel in its way to that of Kepler 
when he found that the positions of the planets conformed 
to a numerical law. Having a series of larve apparently 
of the so-called Coronis (Hrichthus) minutus, of which the 
youngest measured 4°16 millimetres, the second 5:29 mm., 
the third 6-49 mm., and the fourth 10-21 mm., he observed 
that if 4-16 is multiplied by five-fourths, and the result 
by five-fourths, and so on, the resulting series of numbers 
is 
(1) 4-16, (2) 5-20, (8) 6-50, (4) 8-13, (5) 10-16, 
which corresponds as exactly as need be with the series of 
larvee, allowing for the absence of the fourth stage. It is 
highly improbable that larvee bearing a general resem- 
blance to one another would have this curious numerical 
relationship unless they also had a very near relationship 
by blood likewise. Professor Brooks considers that ‘the 
free prolonged larval life has brought about modifications 
which have no reference to the life of the adult, so that 
the larvee differ among themselves more than the adults 
do.’ By reason of their small size and great transparency 
some of these larval forms are very suitable and interest- 
ing objects for the microscope. 
The following list will show the names attached to 
the young forms of the different genera :— 
22 
