1854.] ON PRESERVING THE BALANCE BETWEEN ANIMAL AND VEGETABLE ORGANISM. 



309 



front towards the room and the observer was constructed of 

 plate-glass, the whole being set in a stout framework of zinc, 

 and cemented with what is known under the name of Scott's 

 cement, and which I have found to answer the purpose most 

 admirably. Within this tank were arranged several large pieces 

 of rock-work, thrown into an arched form, and other fragments 

 •were cemented in places against the slate at the back and ends, 

 and at parts along the water line, so that the creatures could 

 hide themselves at pleasure; a short beach of pebbles was also 

 constructed in order that shallow water could be resorted to if 

 desired. The whole tank was covered with a light glass shade 

 to keep out the dust and retard evaporarion. 



With the sea water obtained in January, 1852, I have been 

 working without cessation up to the present time, agitating and 

 aerating when it became foul during the unsuccessful experi- 

 ments on the sea-weeds, but since then it has been rarely ever 

 disturbed; the loss which takes place from evaporation being- 

 made up, as before stated, with rain or distilled water. 



For a considerable period, after commencing these experi- 

 ments, I was much troubled to obtain living subjects in a 

 healthy condition, but having alluded to this, and the success 

 of my investigations, in a short notice appended to a paper 

 published in the "Annals of Natural History" for October, 1852, 

 my friend, Mr. P. H. Gosse, who was then sojourning at Ilfra- 

 combe for his health, offered in the kindest manner to supply 

 me with materials, and from that period he has always most 

 heartily responded to my wants. It must not be imagined for 

 a moment that the beautiful creatures I have thus received have 

 all been preserved alive or always quite healthy. In experi- 

 mental investigations this would be unreasonable to expect, as 

 the very fact of experimenting implies a disturbance of the then 

 state of things. Besides which, from want of a sufficient know- 

 ledge of natural history, from want of forethought and experience, 

 and other causes, I have lost many very fine specimens; and as 

 the detail of these losses may prevent the occurrence of the like 

 annoyances to others, I shall venture to occupy your time for a 

 short period with their histoiy. 



My greatest loss arose from too great anxiety to transfer the 

 collection I had preserved in healthy condition to the end of 

 December, 1852, into the new tank. As soon as it arrived 

 from the maker's I lost no time in introducing my numerous 

 family to their new abode, and dearly I paid for my precipitancy, 

 for on the next morning I found many of my most beautiful 

 specimens dead; thus Host two fine Holothurias (H. Pentactes), 

 a small freckled Goby ( Gobius minutus), a beautiful little Pipe- 

 fish (Syngnathus lumbriciformis), and several others, and on 

 opening the door of the case the cause of this mortality was at 

 once evident, — an iridescent film of oily matter was floating on 

 the surface of the water, arising from the paint with which the 

 angular joints and edges of the small tank had been colored not 

 having become sufficiently hardened. 



Another source of loss arises from the several creatures attack- 

 ing and devouring each other, and therefore it becomes a point of 

 great importance — and highly necessary to be carefully observed, 

 where their preservation is an object— to ascertain what 

 varieties may be safely associated in the same tank; as, for in- 

 stance, I have found that the Shrimps, and Prawns attack, and 

 very soon devour, all the larger varieties of Corallines and Polyps, 

 Sabellas, Serpulse, Rock-bores, Cirrhipeds, some of the Annelids, 

 many of Bivalve and Univalve Mollusks that are unprotected by 

 an operculum, or have no power of closing their valves. The 



instances which have come under my own immediate observation 

 have been the destruction of the Pholas dactylus, Saxicava 

 rugosa, CyprSea Eruopcea, and several specimens of Sabellte, 

 Serpulse, C'oryne sessiiis and many others. 



The common Crab (Cancer Mances) is likewise a most de- 

 structive agent; and the tribe of rock-fish, the Blennies, Gobies, 

 &c, are also most voracious, devouring all the varieties of 

 Cirrhipeds, Corallines, Polyps, Annelids, &c. ; they will also 

 also attack the shrimps and prawns, and even seize upon the 

 horns of the periwinkle, which they bite. If the mollusks do 

 not keep a very firm hold of the rock or tank sides, they are 

 rapibly turned over by these fish on their backs and lie help- 

 lessly exposed to their attacks.* It is doubtless their seeking 

 food of this kind which causes these little fish to be so generally 

 found in the shallow rock-pools of the coast, in consequence of these 

 ravenous propensities I have been obliged to establish several 

 small tanks, and imitation rock-pools, so as to separate these various 

 depredators from each other: thus in one I have varieties of 

 Actinia, Shrimps, Nudibranchs, Holothurias, and some' Anne- 

 lids; in a second the rock-fish, as the Blennies, Gobies, Cottus, 

 with Crabs and Aetinice; in a third Corallines, Annelids, 

 Polyps, Rock-borers, Sabellse, Serpulse, Holothurias, and 

 Actinia. 



Another curious instance of loss I may detail which has quite 

 recently occurred, and which may prove interesting; it was in a 

 small rock-pool containing Blennies, Gobies, Crabs, &c. I had 

 procured two live oysters for the purpose of feeding my numer- 

 ous small fry in these Vivaria, and one of these having proved 

 ample for the purpose of one meal, the other was placed on the 

 sandy bottom ; on the ,second day after this, the oyster was ob- 

 served to have opened the valves of his shell to a great extent, 

 which were afterwards seen closed, but a small Gobius Niger, 

 inhabiting the pool, could no where be seen. The day after 

 this the oyster was opened for the general feeding, when lo ! 

 within the shell was found the unfortunate Gobius, quite dead. 

 Whether this little gentlemen had been attracted within the trap 

 by curiosity or the ciliary motion of the oyster, it is impossible 

 with certainty to say; but that he must have seized on some 

 sensitive part of the oyster is more than probable, so as to have 

 caused such a rapid closing of the shell as could entrap so active 

 a burglar. 



Another important point is the gravity of the sea -water; this 

 should be very carefully regulated, for it must be borne in mind 

 that many of the marine creatures are supplied by a permeation 

 of water through their tissues or over their delicate and beauti- 

 ful organs. The specific gravity should not rise above 1026 at 

 60° Fahr., and a small hydrometer should be introduced at short 

 periods to ascertain that this point is not exceeded, particularly 

 during the hot months of summer. The reduction to this 

 gravity can be readily effected by the addition of rain or dis- 

 tilled water. Many of the creatures will of themselves afford 



* Since the reading of this paper at Hull I have received a Bienny 

 of larger size, being about 3 £ inches in length, and although it has 

 become so tame that it will allow itself to be touched by the hand and 

 takes its food from the fingers, yet its destructive propensities are so 

 great, that it very soon killed four small Crabs ; and to save three 

 others of rather a larger size, I have been obliged to remove the Blenny 

 to a rock-pool in association with his own species and a few Aetinice. 

 The only refuge the poor Crabs had was to bury themselves in the 

 sand, and whenever they attempted to move out of their refuge they 

 were immediately pounced upon and only escaped by burrowing 

 rapidly again. . 



