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 in 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 larvee apparently 

 of the so-called Coronis (Ericlithus) 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, (3) 6-50, (4) 8-13, (5) 10'16, 



which corresponds as exactly as need be with the series of 

 larvffi, allowing for the absence of the fourth stage. It is 

 highly improbable that larvae 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 



