1884.] PROF. F. J. BELT. ON HOLOTHUROIDS. 565 



pointed out at the time in ' Nature,' ' about as much had been 

 expelled as would occupy the greater part of the cloacal cavity. The 

 information forwarded to me by Mrs. Fisher, and reported in the same 

 journal ", is further evidence that the Holothurian is capable of 

 emitting threads which are disagreeable to the human skin at any 

 rate. 



The histological character of these tubes has been so fully 

 worked out by iM. Jourdain and Dr. Hamaun in the essays to which 

 reference has already been made that it is unnecessary here to enter 

 into a detailed account. I have to say, however, that what has most 

 struck me in the tubes of //. nigra has been the great abundance of 

 the connective tissue. When a tube has been drawn out to its 

 utmost tenuity, so fine indeed as to be almost invisible to the naked 

 eye, it is seen under a magnifying-power of 500 diameters to consist of 

 several fine fibres ; a somewhat thicker portion differs only in having 

 the fine fibres more closely packed together. It seems, then, to be 

 pretty clear that the elongation of the threads is due to the uncoiling 

 of the connective-tissue fibres. When thus uncoiled they appear to 

 have no outer epithelial coating, and it is therefore diificult to 

 understand how they can be sticky if tlie glands figured by Hamann 

 have the function that he ascribes to them. This is a point, 

 however, that can only be worked out with living specimens, the 

 threads in situ, extended, and elongated being severally and compara- 

 tively examined. 



In all the specimens whose intestinal tracts were examined these 

 organs were found to have contents formed of a slaty-grey pultaceous 

 mass, clearly made up of decomposing material ; I got no such 

 evidence of the character of the food as was presented to Mr. 

 Peach. 



With regard to the name that should be applied to the Cotton- 

 Spinner, the Rev. Dr. Norman informs me that he is of opinion 

 that H. nigra is a synonym of H. poli of Delle Chiaje, or //. tuhulosa 

 of Sars. I cannot, however, in fresh, any more than in specimens 

 long since preserved in spirit, detect the large spicules in the 

 suckers by which the Mediterranean species is, as is well known, to 

 be detected. 



I am greatly indebted to the reverend naturalist for reminding me 

 that Holothuria intestinalis was dredged in the Minch by Forbes 

 and Goodsir in 1850 •\ and by himself in the same locality in 186G ^ ; 

 so that " H. nigra" has a fellow in the British Seas. 



^ Aug. 7, 1884. p. 335. 



2 June 2fi, p. 193. 



3 Traus. Roy. Soc. Eclinb. xx. p. 309, pi. ix. fig. 1. 

 * Rep. Brit. Assoc. 1866, p. 195. 



