370 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
come about that the imaginal form is exceedingly different from the 
Jarval. This has necessitated great changes in the muscular system. 
It is easy to see that in this evolution many muscles must have reached 
a stage where, if they were to be useful in the imago, they must be 
stronger, or their attachments must be shifted, or they must be changed 
in some other manner, which would necessitate a greater or less meta- 
morphosis. In this metamorphosis nothing could be more probable 
than that there should be, first, a proliferation of the nuclei, second, a 
longitudinal splitting of the original fibre into as many new fibres as 
were needed, and, if an extensive metamorphosis was required, a de- 
struction of the original fibrillae and the formation of new fibrillae by 
the undifferentiated sarcoplasm remaining. Such is the metamorphosis 
which has been described in the present paper for Coleoptera, and I can 
conceive of nothing simpler or more probable. 
The presence of degenerating muscles is quite as easily explained. 
- In the development of holometabolic insects, it must have happened 
many times that a muscle which was useful in the larva became function- 
less in the imago. It is evident that the ultimate fate of such a muscle 
would be degeneration at the end of larval life. The method of degen- 
eration might be different in different cases, but no one can deny suc- 
cessfully that such muscles would exist, though Berlese has attempted to 
do so. The converse of this might also be expected, that is, muscles 
which are useful in the imago but functionless in the larva. Such 
muscles would tend naturally to be retarded in their development until 
they came to be muscles newly formed in the pupa ; but in their final 
development they would arise from the cells which had previously 
formed them. How it could come about that these muscles of new 
formation in the pupa should be developed from cells furnished by the 
degenerating muscles of other parts of the body, as Berlese states, is 
something which I cannot understand. 
From what has been said, it is evident that there is little doubt as to 
the incorrectness of Berlese’s main idea in other groups of insects, as 
well as in Coleoptera. 
Needham’s ( :00) statement that the nuclei of fat cells become associ- 
ated with the developing muscles, does not seem probable. The develop- 
ment of such highly specialized cells into a tissue of such an entirely 
different nature, is an exceedingly rare phenomenon. Nothing that 
would indicate such a development has been seen in the present 
study. 
