461 



that the fat-body disappeared only very slowly, and that many 



of the fat cells persisted even in the imago. / / 



In Nasonia there is a, total absence of phagocytic destruc- 

 tion of the food-laden fat cells. 



Several investigators have^ described a development in 

 Calliphora of new fat cells for the imago. Weismann (1864) 

 was the first to notice it; Berlese (1899-1901) examined the 

 process more closely, and concluded that the imaginal fat 

 cells were developed by the differentiation of the "spheres 

 of granules." This conclusion is the more remarkable when 

 it is remembered that these bodies were regarded by Berlese 

 not as gorged leucocytes, but as disintegration products of 

 larval cells. Henneguy (1904) adopted this view, but regarded 

 the "spheres of granules" as leucocytic in nature. 



According to Supino (1900), on the other hand, the fat 

 cells arise from certain mesenchyme cells, and Perez (1910), 

 in support of this view, figures a number of embryonic 

 imaginal fat cells. 



The observation that a new development of fat cells, 

 whatever the nature of the process, does occur, seems to be 

 well established. In Nasonia, however, I could observe no 

 indication whatever that this took place. It is perhaps useful 

 to point out that the cells of the dorsal abdominal glands 

 above described show a remarkable resemblance to young 

 fat cells, but never develop into these. 



The Function of the Fat-h'ody. 



Although the fat-body is a highly characteristic tissue and 

 occupies so large a portion of the insect, yet its function has 

 been rarely investigated, and is but little understood. It is 

 beyond the scope of this paper to examine this question 

 except in so far as it has a bearing on metamorphosis. 



It seems probable that the fat-body of Nasonia exhibits 

 a limited phagocytic activity; Poyarkoff has seen it in 

 Galeruca, and in Nasonia. it appears also to be present. 



Berlese regarded the fat cells as intimately concerned 

 with nutrition; food passed through the walls of the intes- 

 tine, and was absorbed in an apparently solid state into the 

 fat cells. Migrating inwards it came into the neighbourhood 

 of the nucleus. Then it migrated outwards again, and was 

 peptonised during its progress within the cell. The food was 

 seen in the form of the large and small grains which are so 

 prominent within the fat cells; the pseudonuclei, Berlese 

 regarded, without any evidence whatever, as the enzyme, 

 which brought about this hydrolysis. 



In 1889 P. Marchal observed that treatment of the fat 

 cells with acids would cause the appearance of uric acid 



