48 



in the fluid contents of the A^acuoles, numerous fine 

 granules of excreton^ material (fig. 19) ; these granules 

 increase in size, some much more rapidly than 

 others, and they ultimately take the form of rounded or 

 oval concretions. After excretion has been going on for 

 some time, the fat-body takes the form of an irregular 

 protoplasmic meshwork, in which cell boundaries are not 

 discernable, and nuclei are distributed at various intervals, 

 and the spaces enclosed within the meshes are filled with 

 fluid which contains the excretoiy granules held in 

 suspension. The process of excretion is generally most 

 active in the central portions of the larger masses of fat- 

 body, and the cells of the latter ultimately break down 

 and completely liquefy, with the exception of those 

 situated around the periphery (fig. 20). 



The excretory concretions are unaffected by the action 

 of water, alcohol, ether or toluol, but are readily soluble 

 in acids, and are consequently absent from preparations of 

 animals fixed by acid-containing reagents. They are best 

 seen in animals which have been killed and fixed in strong 

 alcohol. They are of a crystalloidal nature, faintly 

 yellowish in colour and very eosinophilous. Their 

 chemical composition is uncertain, and they do not exhibit 

 any indications of lamination or other structure. 



Sommer (23) has given some attention to the con- 

 cretions found in the fatty body of Tomocerus phnnheus. 

 In this species they are often of large size and are easier 

 to study than those of Aiinrida. They are dirty white in 

 colour when viewed with reflected light, and pale green 

 and shinins' with transmitted light. In their structure 

 they are laminated like starch-grains, and sometimes 

 exhibit radial lines in addition. They are unaffected by 

 water or alcohol, but dissolve in acetic, hydrochloric or 

 nitric acids, accompanied by an evolution of gas. Each 



