THE CATERPILLAR AND THE MOTH 



organs by means of enzymes produced in the nuclei of the 

 cells. The tat cells thus take on the function of a stomach, 

 converting the materials dissolved in the blood into forms 

 that the growing tissues can assimilate. During this time 

 the masses of fat tissue that compose the fat-body of the 



f 



O 



■/■"" 



/ 



' r<- °' 



Fio. 160. Bodies in the blood of a young pupa of the tent caterpillar 



a, a free fat cell, containing large oily fat globules, and small proteid granules; 



b, <-, fat cells in dissolution; d, free proteid granules in the blood, and f, fat 



globules liberated from the disintegrating fat cells;/, blood corpuscles 



larva have broken up into free cells, and these cells, 

 vacuolated with oil globules and later charged with pro- 

 teid granules, now fill the blood. 



The interior of the moth pupa, or chrysalis, shortly 

 after the larval skin is shed, contains a thick, yellow, 

 creamy liquid. In it there may be discovered, however, 

 the alimentary tract, the nervous system, and the tracheal 

 tubes, the latter filled with air; but all these parts are so 

 sort and delicate that they can scarcely be studied by 

 ordinary methods of dissection. 



The creamy pulp of the pupa's body, when examined 

 under the microscope, is seen to consist of a clear, pale, 

 amber-yellowish liquid full of small bodies of various 

 sizes (Fig. 160), which give it the opaque appearance and 

 thick consistency. The liquid medium is the blood, or 

 body lymph. The largest bodies in it are free fat cells (a); 

 smaller ones are probably blood corpuscles (/); and the 



3°3 



