BIOLOGICAL STUDIES ON INTRACELLULAR BACTERIA. 143 



Philiptschenko (1907) studied the physiology of the fat body 

 in Blattela. He did not mention the intracellular organisms, but 

 found glycogen, proteins, fats and urates stored in great quanti- 

 ties especially in young animals. 



From all of these facts, it is easy to assume that the symbionts 

 assist in the carbohydrate and protein metabolism through en- 

 zyme secretion. Of course, the catalase may serve an oxidizing 

 purpose, but I do not attach much weight to such a statement 

 for the reason that protoplasm generally will give this as well as 

 the peroxidase reaction in most cases. Nor do> I lay any em- 

 phasis on the invertase found in the Pcriplaneta organism. It 

 may serve a purpose, but this is not evident. 



4. CONCLUSIONS. 



In speaking of the intracellular organisms of insects, the word 

 symbiont has been used rather freely in the literature. I have 

 also made use of the word more for the sake oi convenience than 

 because I am convinced that we are confronted with true sym- 

 biosis. From the morphological studies presented by others, and 

 from my own work it is a great temptation to refrain from think- 

 ing of a symbiotic relation. From my experiments it is easy to 

 assume that the insect derives some benefit from the organisms 

 as digestive organs, but what possible benefit can the micro- 

 organisms derive? Buchner's suggestions that the intracellular 

 organisms are benefited by being protected within the insects 

 from the drastic atmospheric influences of heat, cold, desiccation, 

 etc., are a little far-fetched. Nor does Buchner's view that the 

 organisms are also assured constant nourishment and oppor- 

 tunity to propagate appeal to me. Millions of bacteria and other 

 organisms not found in the cells of animals manage to live and 

 propagate just as well if not better. It is also necessary to remem- 

 ber that the insect tissue or serum must produce some powerful 

 inhibitor in order to hold the propagation of the microorganisms 

 within a reasonable limit, otherwise the host would be killed. 

 The presence of an inhibitor is surely a handicap in the struggle 

 for existence. 



I think the interesting relations discussed had their origin in 

 true parasitism, possibly, in disease. During an early period the 



