March 8, 1883] 
NATURE 
433 
is one of great difficulty, I will only repeat what I formerly said, 
that ‘additional observations are much wanted at high levels,” 
and I might have added, at small elevations also, 
I have tabulated as above the results given by my two 
formulze and by that of Mr. Archibald, from which it appears 
th 
that my first formula, viz. v=V \/ ,agreesmore nearly with 
the recorded results of velocity at Arthur’s Seat than any of the 
Fh 
others, while my second formula, /= Wess best with my 
first observations of pressure. 
Edinburgh, February 17 THOMAS STEVENSON 
The Supposed Coral-eating Habits of Holothurians 
In glancing through my back numbers of NATURE my atten- 
tion has been drawn to a letter on the above subject by Mr. H. 
B. Guppy, published in the issue dated November 2, 1882. 
Quoting the late Mr. Charles Darwin’s famous work on ‘‘ Coral 
Reefs,” where it is stated at p. 14, on the authority of Dr. J. 
Allan, that Holothuriz subsist on living corals, he recounts the 
results of his investigations made on the reefs of Santa Anna 
and Cristoral, with the object of putting such statement to the 
test. As the upshot of his experiences he writes that he has by 
no means satisfied himself that Holothuriz do subsist on living 
coral. In no instance did he meet with a single individual 
browsing on the patches of living zoophytes, the two species 
observed being indeed found living only in the plots of detritus 
or dead coral matter that flanked the growing masses. Mr. 
Guppy gives an approximate estimate of the amount of coral 
sand daily voided by an individual Holothurian, but adduces no 
evidence as to the manner in which such hard matter is taken 
into its body. This phenomenon indeed he apparently did not 
witness ; nor, so far as I am able to ascertain, has any other 
investigator brought forward any positive testimony in this 
direction, 
Through my cultivation of Holothuriz in company with 
various other Echinoderms a few years since in the tanks of the 
Manchester Aquarium, and also more recently in the Channel 
Islands, I find myself in a position to suj ply this hiatus in our 
knowledge of their life economy. ‘The two species that were 
more particularly the subject of my observations included the 
large, dark purple Cucumaris communis, derived from the Cor- 
nish coast, attaining, in its fully extended eccndition, a length of 
from eight to twelve inches, and the white or dirt; yellow variety 
of Cucumaria pentactes, that rarely exceeds balf these dimensions, 
The oral tentacula in both of these species are largely developed, 
taking the form of ten extensively ramifying pedunculate plumose 
or dendriform tufts stationed at equal distances around the oral 
opening. It is with these organs that the food substances are 
seized and conveyed to the alimentary system, though in a man- 
ner totally distinct from what obtains in other tentaculiferous 
animals, such as a sea-anemone, tubiculous annelid, or cuttle- 
fish. When on the full feed it was observed indeed that the 
tentacles of the Holothurian were in constant motion, each 
separate dendritic plume in turn, after a brief extension, being 
distally inverted and thrust bodily nearly to its base into the 
cavity of the pharynx, bearing along with it such fragments of 
sand and shelly matter as it had succeeded in laying hold of. 
No consecutive order was followed in the inversion of the 
separate tentacles, that which at the moment had secured the 
most appetising morsel gaining seemingly the earliest entrée, 
But little time was lost in this feeding process, for no sooner 
was one tentacle everted than another was thrust into the gullet, 
and so the meal continued, as not unfrequently observed, for 
several hours together. To furnish a fitting simile for this 
anomalous phenomenon of ingestion, one might imagine a 
child provided with ten arms, after the manner of ancient 
Buddha, grasping its food with every hand and thrusting it 
in a quick and continuous stream down its throat, the hands and 
arms with every successive mouthful, not stopping at the 
mouth, but disappearing up to or above the elbow within 
the visceral cavity. That the Holothuriz are not devourers 
of living corals is shown not only in connection with the 
data just recorded, but from the fact also that several of 
these animals were kept in a tank containing sea-anemones 
and corals (Balanophyllia verrucosa) without their interfering 
with them in any way, or manifesting alimentative functions 
other than those just described. All that they require for their 
nutrition is evidently derived then fron the coral or shell debris 
with which they are customarily associated, At first sight this 
material would appear to be in the last degree adapted for the 
sustenance of such highly-organised animals, but, as may be con- 
firmed at any time by the investigation of like conditions in 
aquaria, it will be found that shell-sand, gravel, and all other 
debris forming the superficial layer at the bottom of the water, 
when exposed to the light, is more or less completely invested 
with a thin pellicle of Infusoria, Diatoms, and other microscopic 
animal and vegetable growths. It is upon these minute crganisms 
that the Holothuriz feed, swallowing both them and the shelly 
or other matter upon which they grow, much in the same way as 
we might subsist on cherries, swallowing stones and all—the 
nutritious matter in the case of the cherries being in much 
greater ratic—and the Echinodermata having the advantage over 
us that they have no vermiform appendage to their alimentary 
system to jeopardise their safe indulgence in such stone-swallow- 
ing propensities. Most probably, but this as a fact I did net at 
the time take steps to determine, the shell or coral debris, with 
its investing organisms conveyed to the mouth, is triturated by 
the characteristic teeth that arm the pharynx into one homo- 
geneous mass, which, after the extraction of all nutritious sub- 
stances, is discharged in the form of sandy pellets at the 
opposite extremity. At all events, the phenomenon of food 
ingestion as witnessed and here described amply accounts for 
the relatively prodigious quantities of shell- or coral-sand that 
the Holothuris have been ob-erved to void by Mr. H. B. Guppy 
and other writers. 
Data of interest concerning the feeding processes of various 
other Echinodermata were noted by me at the Manchester 
Aquarium. Two species of Echini—Z. miliaris and EZ. lividus 
—throve well, and devoured large quantities of the seaweed, 
Ulva latissima, thus demonstrating their essentially herbivorous 
tastes, while the common Sand-star, Ophiura tex‘urafa, eXx- 
hibited peculiarly interesting habits. These were kept in a 
shallow tank with a sandy bottom, and, except at feeding-time, 
were but rarely vi-ible. No suoner, however, had a few small 
pieces of chopped fish been dropped into the water and settled 
to the bottom than their snake-like arms appeared above the 
sand in all directions, next their entire bodies, then a general 
scramble ensued for the provided food. This was conveyed to 
the creatures’ mouths with the aid of the flexile arms, one of 
which was dexterously twisted round the selected fragment—as 
an elephaut might use its } roboscis—and the morsel then dragged 
beneath the body with its central oral aperture, or rather the 
body dragged on top of it. Pher.omena of corresponding interest, 
did space yermit, might be related of numerous other species, 
but the foregoing will suffice t» illustrate the amount of know- 
ledge that may be gained, and gained in no other way, concern- 
ing the habits and life-histories of marine organisms by their 
intelligent study in the tauks of an aquarium, 
Apropos of this subject of aquaria, it will interest all biologi-ts 
to know that the long-hoped for opportunity has at last arrived, 
or is about to arrive, of securing to the nation an aquarium 
suited in all ways, in both position and equipments, for the 
conduct of scientific pisciculture and biological research. In- 
cluded in the buildings now in course of erection for the forth- 
coming International Fisheries Exh bition is a fine series of 
marine and freshwater tanks, having such substantial construc- 
tion and perfect mechanical arrangements, that it is proposed to 
leave them standing after the close of the Exhibition, their final 
destiny having alone to be decided on, ‘The close contiguity of 
these tanks in the Western Arcade of the Horticultural Gardens 
to the exi-ting Museum of Economic Pisciculture immediately 
suggests the appropriateness with which they might be incorpo- 
rated and more fully developed in conjunction with that Museum, 
or with the biological department of the Science Schools on the 
opposite side of the road. Asan appanage of the last-named 
insti‘ution, it is indeed almo t impossible to prognosticate the 
important 7é/e t! is aquarium might be adapted to fulfil. Leaving 
a sufficiency of tanks for public exhibition, the remainder might 
form an efficient depot or inland zoological station for both 
supplying the class-rooms and for placing at the disposal of 
original investigators facilities hitherto unprecedented in this 
country for making themselves acquainted with the structure, 
habits, and developmental histories of organisms pertaining to 
every branch of marine biology. It is at all events most earnestly 
to be desired that steps will be taken at the right time by the 
proper authorities to turn to good account so magnificent and 
rarely recurring an opportunity. W. SAVILLE KENT 
Buckland Fish Museum, South Kensington, February 21 
