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, sucli 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 tlie 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. 



