2/8 FRANCIS A. HULST. 



was found necessary, to insure good fixation, to puncture the 

 chitinous integument before immersing in the respective fluids. 

 Specimens punctured, or clipped in two or three different places 

 with fine-pointed scissors, and then plunged at once into hot 35 

 per cent, alcohol gave very good results. Specimens killed and 

 preserved in formalin gave poor fixation, and those killed in 

 cold alcohol were also inferior to the above. 



Serial sections cut three microns and stained on the slide by 

 the iron-hsematoxylin method were made and studied in the vari- 

 ous stages of development. Bordeaux-red made an excellent 

 counter-stain for these sections. To supplement these, series 

 were stained in Delafield's haematoxylin and eosin. 



HISTORICAL. 



Although the subject of metamorphism has excited the interest 

 of naturalists of all ages, for definite work upon the problem of 

 the internal phenomena, one need go no further back than the 

 work of Weismann in 1864; while it was that of Metschnikoff 

 ('83), introducing the idea of phagocytosis, that gave the incen- 

 tive for closer and more thorough investigation of the subject. 



Weismann studied the postembryonic development of Musca 

 vomitoria and called attention to the degeneration of the tissues 

 of the pupa. He introduced the term " histolysis " to indicate 

 the process of change which took place. According to him the 

 degeneration is of a fatty nature and the resulting mass mingles 

 with the blood whose elements have also degenerated forming 

 altogether a thick fluid (Brei). Fragments of the mass become 

 isolated, surround themselves with a membrane, take on a gran- 

 ular appearance, lose their fatty particles and acquire a nucleus. 

 These conglomerates of detritus were termed granular spheres 

 (Kornchenkugeln), and to them he attributes the formation of 

 free cells dc uovo, and believes they furnish material for the con- 

 struction of new tissues. 



Ganin ('77) studied the muscidae and agrees largely with 

 Weismann. He believes that the products of degeneration serve 

 in the formation of new organs only as nutritive substance. He 

 demonstrated the existence and composition of the imaginal discs, 

 which persist as embryonic rudiments in the various organs 



