154 F. X. WILLIAMS 



In later stages they often mass together, thus somewhat re- 

 sembling a tissue. They are intimately connected with the fat- 

 body at certain stages and evidently play an important part in 

 the histolysis of muscles, especially those of the thorax. In 

 this region they apply themselves closely to the muscle tissue, 

 though none was found penetrating or ingesting it. Except for 

 their smaller size and the often more irregular shape of their 

 nuclei they much resemble incipient fat-cells. They are natu- 

 rally more abundant in the pupal stage than at any other time. 

 Blood-cells were very seldom found in the process of division, 

 and when in this condition it was difficult to determine the kind 

 of haemocyte which was under observation. 



The partially investing cap as well as the fat haemocytes 

 seem to be instrumental in the breaking up of the fat-body, 

 either into separate cells, as is largely the case in the luminous 

 tissue, or into scattered food particles for the various organs, 

 as was noticeable in the head and thorax. It is noteworthy 

 that in the case of the photogenic fat-spheres the investment is 

 usually on the side next to the alimentary tract, so that when 

 the fat-cells are liberated they are able immediately to migrate 

 to the body wall and there form the photogenic layers. By the 

 inflection of the cap or investment, the fat-sphere is squeezed 

 or constricted at that point till the thin membrane opposite can 

 no longer withstand the pressure, when as a result the fat cells 

 are ejected in masses (fig. 24), and presumably also singly. The 

 pressure exerted often serves greatly to attenuate the nuclei, 

 but no cell division could be detected during the process. Very 

 rarely, and then only in the case of a thoracic fat-sphere, were 

 the cells seen to be liberated through a rupture of the cap. 

 Vogel ('13) has described the breaking up of the fat-body in 

 Lampyris noctiluca, to form the photogenic tissue. The envelope 

 of the fat-body is ruptured, probably through the activity of 

 neighboring leucocytes, and from the old membraneless nuclei 

 of the fat cells arise new ones which are richer in chromatin and 

 possess a distinct nuclear membrane. One might say that the 

 nuclei regenerate, for here there is considerable mitosis, espe- 

 cially on that side of the photogenic fat-bodies which is nearest 

 the hypodermis.) 



