BREED: METAMORPHOSIS OF THE MUSCLES OF A BEETLE. 359 
changes in the muscles of the intestine. I have studied especially the 
region of the proventriculus, where the muscle layers are well developed. 
No differences were discovered between the changes of the muscles of this 
region and those of the remainder of the intestine. Two general figures 
are given. Figure 51 (Plate 7) is a portion of the wall of the proventri- 
culus in a larva about to pupate, and Figure 52 is a similar figure from 
an old pupa. The muscle fibres are found in two layers: a circular layer 
inside (mu. crce.), and a longitudinal layer outside (mu.lg.). Their 
structure is similar to that of the other larval muscle fibres, except that 
the nuclei are more frequently found at the centre of the fibres and that 
Cohnheim’s areas are arranged similarly to those shown in Figure 20 
(Plate 6); this particular figure, however, is not from one of the larval 
fibres. The principal difference between the destructive changes in these 
muscles and in those of the leg type is, that they are still slower in 
being completed than the latter. The larval fibres rarely, if ever, divide 
lengthwise to form new fibres, those in the larva being apparently as 
numerous as those in the imago. The tracheal cells are slower in mak- 
ing their appearance, and only a few are found in this region at the time 
of pupation (see Figure 51, which does not show any of them) ; whereas, 
even before this time, they are numerous in the regions of the other 
metamorphosing muscles. Compare Figure 14 (Plate 6) and Figure 49 
(Plate 7), which are from younger pupae than Figure 51. The intestinal 
muscles show cross striation much longer than any of the other metamor- 
phosing muscles, as the striation does not disappear until the pupa has 
undergone nearly half of its development. Longitudinal fibrillation dis- 
appears almost as quickly, and thus a structureless stage, shown in 
Figure 52 (mu. cre.), is reached. 
During all the time in which the destruction of the contractile ele- 
ments is taking place, the muscle nuclei show no apparent changes. 
No cases of amitosis have been seen, though they are common in the 
other metamorphosing muscles; nor is there any evidence of degenera- 
tion and phagocytosis such as Deegener (:00) states that he finds. It 
seems as if Deegener’s statement, that there is phagocytosis of these 
muscles, such as Kowalevsky (’87) and Van Rees (’88) found in Mus- 
cidae, must be strongly questioned. For, in the first place, both Rengel and 
I have failed to find evidence of it in Coleoptera. Secondly, it is evident 
on reading Deegener’s paper that this statement is based more on infer- 
ence than actual observation. No satisfactory figure nor description is 
given of the phenomena which take place when the leucocytes attack 
the muscles. Apparently the only ground for the statement is that he 
