154 SEA-SIDE STUDIES. 



Perhaps nothing has excited more surprise on the 

 part of the public, and nothing has been more unani- 

 mously believed by anatomists, than the hypothesis 

 that certain minute organs found in all Polypes, and 

 variously styled thread- cap sides, filiferous-capsides, or 

 urticating cells (Plate III. fig. 5), are organs of urtica- 

 tion, or stinging. The uncritical laxity with which this 

 hypothesis has been accepted may point a lesson. I 

 do not allude to the acceptance of the fact that certain 

 capsules containing threads are found in Polypes ; but 

 to the acceptance of the alleged purpose, or function, 

 of these capsules. The things are there, sure enough ; 

 but whether they serve the urticating purpose, is an- 

 other matter. Ever since they were first described by 

 Wagner,"'' Erdl,t Quatrefages, and Siebold,| they have 

 passed without challenge. They have been detected 

 in the whole group of Polypes, in Jellyfishes, in the 

 papillae of Eolids, and, according to Van der Hoeven, 

 in Planarise ; yet, as far as my reading extends, not 

 one single experiment has been made to prove the 

 function so unanimously admitted, not a single test has 

 been applied to strengthen or controvert what was, 

 indeed, very plausible, but only plausible, not j^^'oven. 

 Accordingly, no sooner did I submit the question to 

 that rigorous verification which Science imperiously 

 requires, than it became clear to me that my illustri- 

 ous predecessors — Wagner, Erdl, Siebold, Quatrefages, 



*Wiegmann's ^rc/wv., 1835, ii. p. 215. 

 t Mueller's Archiv., 1841, p. 423. 

 % Comp. Anat., i. p. 39 (English Trans). 



