INTRAOELLULAR DIGESTION OF INVERTEBRATES. Ill 



possible ; but whether this be so or not, I am convinced that 

 such a history can never be obtained by purely morphological 

 and histological methods, such as those employed by the Hert- 

 wigs in their " Coelomtheorie." 



Since we have seen that the power of intracellular ingestion 

 and absorption is used as a protection against harmful bodies 

 arising within an organism on reaching it from without,^ it 

 follows that septic organisms (Bacteria, Chytridese, Entomoph- 

 tora, and other parasites) are a very old source of trouble in 

 the world ; and perhaps many organs and events, whose signi- 

 ficance has hitherto been overlooked, may find an explanation 

 in this way. I would especially mention the nematocalyces of 

 Plumularia, and the peculiar test of Ascidians. It is evident 

 that instances of prophylactic organs will soon be multiplied, 

 so as to far exceed in number the few I have given. Here is 

 yet another case. On the inner surface of the contractile walls 

 of the excretory organ of Carinaria there are certain "" granular 

 cells," in which a formation of renal concretions is believed to 

 occur, as in the Gastropod kidney. I have, however, been 

 able to prove that these concretions are not formed in the 

 cells, but are really foreign particles taken up by the cells, 

 which are amoeboid, as may be proved by suspending carmine 

 or indigo in the water in which the Carinaria lives. Since 

 the excretory organ pumps water into the pericardial cavity, 

 these cells are posted on its walls to prevent the entrance, with 

 the water, of bodies harmful to the organism. 



The great advances made in Pathological Science during the 

 past few years cannot fail to benefit pure Zoology, which will, 

 in its turn, help to solve the problems of Medicine by esta- 

 blishing a Comparative Pathology, based on the doctrine of 

 Evolution. 



' In this way may be explained the recent observations of Buchner on the 

 action of inflammation on Bacteria (' Die atiologische Tlierapie und Prophy- 

 laxis der Lungentuberculose,' Miischen, 1283, pp. 11 and 12). 



