ANATOMY OF THE EOLIS. 105 



mists it is tlionglit that tliesc tubes are biliary ducts, and 

 perhaps in some species this may be so, but that it is not so 

 in all, I have positive evidence. I was one day examining 

 some Polypes under the microscope, when my attention was 

 diverted by something granular, contractile, indistinguish- 

 able in shape. On extricating it from the branches of the 

 Polype, I found it to be a white oblong jelly-like creature, 

 about the size of a pin's head. Keplacing it under the 

 microscope, I saw that it was an Eolis, but whether of a yet 

 undescribed species, or only the young of some known species, 

 my very imperfect knowledge did not enable me to decide. 

 The extreme transparency of its tissues was such that I 

 could observe it with satisfactory precision. It had only 

 eight papillae on either side, but these were very large, each of 

 the central ones measuring at least a sixth of the whole animal. 

 This was another fortunate circumstance, enabling me to 

 detect the passage of the dark granules which almost filled 

 the cavities, to and fro from the intestine, with which these 

 cavities were in direct communication. All doubt was im- 

 possible : there was the food oscillating from the intestine 

 into the papilla, and back from the papillas into the intes- 

 tine ; and this oscillation, I observed, did in nowise depend 

 on the contractions and expansions of the papillee, but wholly 

 on the contractions and expansions of the body ; for some- 

 times the granules ran up into the cavities when the papilla? 

 expanded, but sometimes they remained in their previous 

 position. 



You see that the papillse are gastro-hepatic organs, or, to 

 speak less technically, that they are parts of the intestinal 



