Digestive Processes in Arachnids. By H. M. Bernard. 433 
it will be seen that they are essentially similar. The presence of 
these food-globules in the peritoneal cells is probably to be attributed 
to the inability of the digesting cells to hold all the food taken m, 
which is therefore passed temporarily into the cells outside the 
alimentary canal as into a kind of storehouse for undigested food. 
Metschnikoff * has already shown in the Ctenophora that endoderm 
cells pass on solid particles such as carmine grains to adjacent meso- 
derm cells. 
The question, then, naturally arises, if these are food-globules why 
are they not digested in these cells as they would be in Amoebae ? 
Examining them carefully to ascertain this point, I was speedily con- 
vinced that a slight digestive process does go on. Here and there 
globules are seen no more clear and homogeneous but finely granular ; 
others are even broken down completely into the typical crystal -like 
bodies which are apparently the invariable remains of such food- 
globules when their assimilable elements have been extracted. Com- 
pared, however, with the immense number of food-globules stored up 
in these cells, only a very small percentage were being assimilated. 
When such extra-enteric digestion does take place, the crystalline 
residue does not pass back into the alimentary canal, but is carried 
away by the blood-corpuscles (fig. 3). What the ultimate fate of 
these blood- corpuscles is I have been unable to ascertain. 
If this description of the phenomena is correct, the life-history of 
these blood-corpuscles is curious. Originating as digesting cells 
within the alimentary canal, they break loose and pass down the gut, 
assimilating the contents of their food-vacuoles during the passage, 
and finally pass out through the wall of the hind-gut and become free 
blood-cells. When in the blood, among other functions, we find them 
carrying away faecal masses from the peritoneal cells which have 
somewhat irregularly digested the food-globules temporarily stored up 
in them. 
I am indebted to my friend Prof. Howes for calling my attention 
to the somewhat similar observations recorded by Kiikenthal in an 
Oligochaetan Annelid ( Tubifex ).f Kiikenthal found the lymph cells 
carrying about brown granules which they obtained from the walls of 
the dorsal blood-vessel and its branches, which latter surround the 
alimentary canal in a close network. When full of these brown 
granules the lymph cells are distinguished by the name of chlora- 
gogen cells, which seen mussed on the above named blood-vessels form 
the brown body thought at one time to be the liver. The brown 
granules undergo a change within the lymph cells ; they are dissolved 
down into minute dark bodies. These dark bodies are finally got rid 
of by means of the nephridia, the tubules of which Kiikenthal describes 
* “ Uber die intracellulare Verdauung bei Codenteraten, Zu l. Anzeig., 1880, 
p. 261. 
t “ Uber die lymphoiden Zellen der Anneliden,” Jenaische Zeitschr., xviii. (1885). 
