Cuvierian ()rr/c/?2,9 0/ Ilolotliuria nigra. 275 



sion. The only object which they do not appear to adhere 

 to is tlie slimy body of the llolothurian itself. 



With regard to the cause of this elongation, all the state- 

 ments known to me in the literature of the subject attribute 

 it to one of two causes, or to a combination of them — (1) to 

 jiqnid being forced into the tube, (2) to an unwinding of the 

 sjnrally wound connective tissue in the walls of tlie tube. 

 Semper (7, p. 139) examined Bohadschia marmorata^ in 

 which ejection of the Cuvierian organs was not observed, but 

 in which they showed power of elongation. A freshly caught 

 animal was quickly cut open, so that the viscera came out of 

 the wound, without the intestine breaking away from the 

 cloaca. When the cloaca was stimulated at the point where 

 the lowest Cuvierian organs were fixed they all shortened 

 themselves by about a half. In the same way they elon- 

 gated voluntarily, and became then very long and at the same 

 time thicker. Ueuce the author concluded that they must 

 possess a contractility of their own and that elongation could 

 only be brought about by an intlux of blood. No blood- 

 vessels, however, were observed, and it is quite certain that 

 none exist. 



Iderouard (3) attributes their elongation entirely to water 

 being forced in from the cloaca. Having studied Ilolothuria 

 catanensi's, he describes them as hollow tubes attached to a 

 dilatation of the res|)iratory tree and provided with sphincters 

 at their orifices. When the water wliich is contained in the 

 dilatation of the respiratory tree is compressed by the eon- 

 traction of its walls it penetrates into the tubes. This can 

 be shown by ligaturing the anus and cutting the body-wall, 

 so as to expose the Cuvierian organs. Certain of the tubes 

 can then be seen to dilate gradually from the base upwards, 

 until equilibrium of pressure is restored. When set free into 

 the surrounding water they dilate by a process analogous to 

 that described above. 



Jourdan (4, pp. 49, 50), on the other hand, attributes the 

 whole process (in //. ivijjatiens) to the stretching and un- 

 rolling of the bundles of connective tissue, commencing at 

 the basilar region. The muscular layers seem to break up 

 and let the connective tissue loose. The tubes are only 

 fe-ticky when ejected. Cuenot (2) steers a middle course, and 

 attributes their elongation within the body (also of //. /'m- 

 putiens) and ejection to pressure of liquid from the cloaca, 

 with Ilerouard; but after they are ejected the spirally wound 

 n)uscles and connective tissue unroll, so that the tube elon- 

 gates, and at the same time tiie external epithelium changes 



19* 



