125 



Deeoekrk (1909) supposes the rigidity of the ehitinous 

 skin to be the cause of the moultings and he thinks (p. 19 

 sqq.): ''that the higher specializeil insects possess a tendency and 

 a will to diminish the number of these moultings. This can only 

 bo achieved by retarding the development between two moul- 

 tings, and so attaining by one eedysis what otherwise could only 

 be attained by many. The more these moultings were reduced 

 in number, the less recapitulations of phylogenetic stages had to 

 be passed by the larva, and so it makes the, impression that 

 phylogenetically its development is retarded, and ontogenetically 

 it rcnmins all the longer in a primitive state, by retardation of its 

 development. Through this, the larva has the opportunity of 

 specializing itself, according its own desire and character. The 

 great difference has ariseii in consequence of a different manner 

 of life, especially the aquatic one. Pupa and subimago are 

 not identical, but they are both primary stages of development, 

 which have remained preserved." 



Bastis (1918) and Cakpester (1913) are both adherents of 

 the subimaginal theory, especially the latter, who has published 

 a short but very interesting treatise, which contains a great many 

 facts and is written with grejit conviction. 



In constructing a theory on the origin of the pupal state it is neces- 

 sary to study the subject from as many different points of view as 

 possible. By Weismann's investigations especially (1863, '64, '66), 

 later on continued by i.a. J. van Kees (1888), MESNiLand Metsch- 

 MKOFF (1900), Bauer (1904), Janet (1909) and Poyarkoff (1910), 

 the attention of the investigators has been turned more to the 

 histological processes and in the first place to the histolysis in the 

 pupal stage, than to the purely morphological problems. Histolysis 

 may be considered to be a secondary phenomenon, but from that 

 it does not follow that the pupa itself is secondary. The larva of a 

 frog is not secondary because its tail disappears by phagocytosis! 

 It is therefore desirable to direct the attention to palaeontology, 

 which has been greatly neglected by many entomologists. On this 

 point I refer especially to the last of the three following writers : 



