Cuvi'erian Organs o/'Iiolothuria nigra. 281 



touchent. L'observation des falts contredit cette raanicre do 

 voir. Les tubes de Ciivier sont simplement des organcs arbo- 

 rescents transformds, eminemeut exteiisibles et contractiles, 

 adaptds a des fonctioiis glaiidulaires speciales." 



At tlie risk ot" being considered by M. Hcrouard as a 

 " partisan of final causes," I must express my opinion that 

 in the Cuvierian organs we have to do with organs of defence. 

 I do not liold this belief because these organs are remarkably 

 sticky, any more than I believe that a pistol is a weapon of 

 defence because it is hollow ; but because I have seen them 

 in action, which M. Herouard does not seem to have done. 

 After denying them a defensive function, M. Hci-ouard terms 

 them glandular organs ; but, as Ludwig (5) remarks, it is 

 difficult to reconcile this idea with their structure, since the 

 glandular layer is separated from the lumen by connective 

 tissue. Moreover, the ejection of these organs in Holothuria 

 nigra is in no way a pathological process, as M. Herouard 

 supposes, but a perfectly normal act. There can be no 

 reasonable doubt, it appears to me, that in the species here 

 under consideration the Cuvierian organs function only as 

 weapons of defence *. Nevertheless it is quite possible that 

 they may not have this function universally in the group of 

 Holothurians and may have primitively served some other 

 function. In fact the Cuvierian organs of BoJiadschia mar- 

 morata^ as described by {Semper (7, p. 139), can hardly be 

 used for defence in the same way as those here described. 



In considering the question it should be borne in mind that, 

 while these organs may be highly developed in one IIolo- 

 thurian, they may be altogether wanting in another closely 

 allied form. Thus they are quite wanting in Holothuria tuhu- 

 losa, which is a close ally of our form. This fact seems to me 

 to go against the idea that they represent in any way a 

 morphological rudiment, i. e. an organ which formerly had 

 some other very diflt'erent function. Their position and mode 

 of growth shows them to be simply outgrowths of the respi- 

 ratory trees. In some Holothurians they are, as is well 

 known, racemose or " traubenformig." In such forms there- 

 fore they would appear to be less differentiated from the 

 remainder of the respiratory tree than in forms like Holo- 

 thuria nigrttj where they are highly specialized. These facts 



* In Naples I was able to observe the large Holothuria sancfori, which 

 emits its organs in the same manner as //. tiiyra. The Cuvierian organs 

 are smaller in this I'orm than in JL niijia, and, owing to the great thick- 

 ness and mu.-cular power of the integument, they are more dirticiiJt to 

 study in the li\ing animal. 



