342 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
of the muscles of the larva. The changes of the muscles are similar to 
those in Lasius, as described by himself (’98). 
Deegener (:00) describes the metamorphosis of the intestine in 
Hydrophilus. His observations on the changes of the intestinal mus- 
culature differ in many fundamental points from those of Rengel on 
Tenebrio. He finds typical phagocytosis, such as Kowalevsky (87) and 
Van Rees (88) found in Muscidae. The phagocytes make their appear- 
ance in the old larvae, engulfing both sarcolytes (muscle fragments) and 
muscle nuclei. They then do not become scattered through the body, 
but degenerate —in larger part at least —in the lumen of the pupal 
intestine. Spindle cells whose origin is uncertain, but which cannot have 
been derived from the nuclei of the larval muscle, appear in the old 
larvae. In the muscle layer of the pupa, the changes are difficult to 
follow on account of the close intermingling of diverse elements. The 
spindle cells give rise to the imaginal musculature, but he does not 
describe the process clearly, nor give figures. 
In the midintestinal region, there are so few phagocytes that they are 
not sufficient to entirely account for the disintegration of the muscles, so 
that, in this case, there must be chemical degeneration as well. The 
source of the imaginal musculature in this region is doubtful, as no 
spindle cells could be distinguished. Deegener thinks, however, that 
spindle cells are present in the closely intermingled elements of the 
muscle layer, and that the imaginal muscles are derived from them. 
Berlese (:00, :01, :02*) speaks of the histolysis and histogenesis of the 
hypodermal muscles in Aphodius and other Coleoptera. He states 
that the larval muscles are dissolved, but that the nuclei resist dissolu- 
tion. These nuclei emigrate from the degenerating larval muscles, 
acquiring cytoplasm and a cell membrane, and thus become “ sarcocytes.” 
By division, the ‘‘sarcocytes” form spindle-shaped ‘ myocytes,” which 
give rise to the imaginal muscles by fusing in rows to form muscle fibres. 
The “ myocytes” at one stage closely resemble leucocytes, so that there is 
a possibility of confusing them; but Berlese, reasoning from his similar 
studies on Muscidae, feels confident that their origin is, as has just been 
stated, from the nuclei of the degenerating larval fibres. 
Needham (:00) states that in Mononychus vulpeculis the fat cells of 
the abdominal region, after getting rid of their surplus food supply, be- 
come associated with the new muscle rudiments, and that their nuclei 
become nuclei of the developing muscle fibres. 
Diptera. The most important of the investigations concerning the 
postembryonic development of insects have been made on Diptera. 
oir erat? 
