438 
Transactions of the Society. 
matter within the blind ends of the tubules was clearly recognized by 
Plateau,* who, however, thought that it was some fatty substance. 
The fact that the granular contents of the Malpighian tubules looks 
white by reflected light, and black by transmitted light, has been 
further recorded by Bertkau. 
Taking, then, further into consideration this very close resem- 
blance between the chalky substance in the peritoneal cells and 
Malpighian tubules of Araneids and the undoubted faecal crystals 
within the gut and stercoral pockets of the Arachnids, I think there 
is a considerable weight of evidence in favour of the interpretation of 
the phenomena here suggested. 
The above-mentioned cases of extra-enteric digestion make it not 
impossible that the processes described by Ktikenthal, and above 
referred to (p. 433), may admit of a similar interpretation. It is to 
be specially noted that the brown bodies taken up by the lymph cells 
appear on the dorsal vessel and its branches, which are directly 
related to the mid-gut. As the contents of these vessels would 
be largely derived from the products of enteric digestion, it seems 
more probable that these brown bodies are food-products than waste 
products. We have, further, the fact that these brown bodies undergo 
a change within the lymph cells very much resembling the change 
undergone by the food-globules when assimilated. 1 have examined 
the chloragogen cells of Lumlricus with an apochromatic oil- immersion 
lens (Zeiss), and though I could not find any of the brown globules 
being dissolved down into black bodies as Ktikenthal describes, yet 
microscopically the brown bodies themselves were quite indistinguish- 
able from the typical food-globules so often alluded to above. The 
suggestion that the function of the chloragogen cells is digestive is 
not new. I think, however, that the observations here described 
justify me in repeating the suggestion. 
There is nothing new in principle in these cases of digestion by 
mesodermal cells. Although the undoubted rule among the Metazoa 
is that the endoderm cells, even from the first digestion of yolk in the 
embryo, undertake the processes of digestion, we have records of 
digestion both by ectoderm and by mesoderm cells. There is no claim 
here put forward of mesoderm cells becoming specialized for digestion, 
at least in the Arachnids, but only that mesoderm cells occasionally 
digest food stored up in them, therein simply reviving the power once 
possessed by their Protozoan ancestors, and still possessed by their 
free phagocyte brethren. 
For the purposes of this paper some young spiders, just hatched 
and clinging helplessly to the nest, were examined. These, when 
seen entire, cleared in cedar or clove oil, show the digesting diverticula 
* Tom. cit., p. 428 (p. 344 : “ Chez tous les Epeires la glande est granitee de 
blanc ou de blanchatre a la surface, fait du a la presence vers le sommet des ccecums 
supcrficiels d’une accumulation de graisse incoloree finement divisee. II arrive 
parfois que cette (jraisse remplit entierement les ccecums de la surfacc ,> ). 
