1884.] PROF. F. J. BELL ON HOLOTHURIA NIGRA. 375 



the mass measured 15 mm., while the body itself was only 40 mm. 

 at its widest. Traced backwards this mass is found to arise from the 

 cloaca ; separated from the investment of connective tissue (which 

 may be in parts pigmented), its free or proximal end is seen to be 

 easily separable into long coiled blind tubes, of which indeed the 

 whole mass is made up. In relation, therefore, and in general struc- 

 ture the tubes are what Johannes Midler called Cuvierian organs K 

 They will be found to offer ns some interesting characters, both from 

 the morphological and physiological point of view. 



In the monograph just cited, the founder of the morphology of 

 the Echinodermata described three types of Cuvierian organs — the 

 caecal, the racemose, and one to which he gives no distinguishing 

 name, and which may perhaps be distinguished as verticillate. It is 

 to the first group that the organs of H. nigra belong ; but they differ, 

 so far as I can learn, from any yet described, by the fact that they 

 are closely united together into a firm bundle. 



This firm union of the tubes into a single mass makes it difficult 

 for us to imagine how single tubes can be emitted. In the woodcut, 

 however, now given, which has been taken from a specimen in which 

 the organ and its parts occupy their original or natural position, it 

 will be seen that a few coiled tubes are lying in the cloaca (fig. 1, cl). 

 Is it not then probable that, on excitement, a suitable contraction 

 separates off this portion of the organ from the rest, and that another 

 expels it to the exterior ? 



It is not to be thought that so small a portion of the tubes would 

 not be of some size in the water, for 2"5 mm. of one of these tubes 

 may, even after nearly twenty years' preservation in spirit, be 

 stretched out to a length of more than 30 mm. ; and this attenuated 

 thread swells up so much in water that, while measuring one 

 division of the micrometer when dry, it occupies seven divisions 

 after treatment with distilled water for ten minutes. We can thus 

 understand that an animal at whom these threads are thrown should, 

 as it attempts to escape, lengthen the threads which, at the same 

 time, coming into contact with the water, would be swollen out 

 transversely as they were extended longitudinally. 



The observations made during recent years on these Cuvierian 

 organs seem to justify a more definite statement as to their function 

 than the supposition of Jaeger that they are renal organs, and to 

 lead to an acceptance of the well-grounded statement of Semper 

 that they are not glandular tubes at all, but protective or offen- 

 sive organs 2 . In this connexion Semper cites Peach's note on the 

 "Cotton-spinner;" and the observations just recorded on the power of 

 increase of length and the influence of water show that he has cited 

 it with justice. The view of Semper, which is shared by Greef, has 

 been recently accepted by M. Jourdan, who, like him, has had the 

 good fortune of being able to work on living and fresh specimens 3 ; 



1 "Ueber den Bau der Ecbinodermen," Abh. Ak. Berl. 1853. 



2 ' Holotburien,' p. J 4(1. 



3 Annates du Musee d'bist. nat. do Marseille, i. Part 2, no. 6. See also 

 O. Hamann, Zeitsebr. f. wiss. Zool. vol. xxxix. 



