284 FRANCIS A. HULST. 



myoblasts the contractile substance seems to disappear as if by 

 digestion and absorption. 



Caullery and Mesnil ('oo) claim a phagocytosis in the meta- 

 morphosis of crustaceans. The leucocytes arrive outside of the 

 muscular substance at a time when there is a degeneration in the 

 muscles as shown by the indistinctness of the striation. The 

 myoplasm passes into a formless mass of remnants of former 

 muscles in the meshes of a protoplasmic network in which state 

 the nuclei resemble amcebocytes. 



Needham ('oo) in studying the metamorphosis of the flag- 

 weevil (Mononyckns vuplieculu} finds an interesting point in the 

 fact that phagocytes do not appear in the destruction of larval 

 tissues until the imaginal stage is entered upon. Then they ap- 

 pear in large numbers in the midst of the fat along the sides of 

 the abdomen. The significance of this is more marked when 

 one considers that the flag-weevil has a complete and rapid 

 metamorphism. 



Breed ('03) gives an account of the muscular changes in Thy- 

 malus marginicollis Chevr. Three groups of muscles receive 

 separate consideration here. One strictly larval, which com- 

 pletely disintegrates and is lost ; a second which metamorphose 

 into imaginal muscles ; and a third which are strictly imaginal, 

 having no counterpart in the larva. These classes present differ- 

 ent characteristics, and the muscles of one class present great 

 individual variation. In the muscles of the second class there is 

 a longitudinal division of the original fibers into several fibers. 

 A destruction of the fibrillae follows until the muscle fiber becomes 

 a structureless mass of sarcoplasm. The number of nuclei is 

 greatly increased by amitotic division. At an early stage cells 

 derived from the intracellular tracheoles are found between the 

 fibers, which eventually give rise to the new tracheoles. In the 

 muscles of the first class he makes two divisions, one of which 

 undergoes a progressive atrophy with no change of the nuclei 

 until the last stages when they undergo a typical chromatolysis ; 

 in the other there is a process similar to that described above for 

 muscles of the second class, i. e., the muscles undergo a change 

 similar to those of the metamorphosing muscles until the stage 

 of reconstruction begins. Trachcal cells are found in both of 

 these cases, more especially in the latter, which the author believes 



