PROF. OWEN ON A NEW SPECIES OF EUPLECTELLA. 121 



for by the solution of the gluten, to wliich act, perhaps, the greater transparency of the 

 soaked fibril might be due. No diminution of diameter or other change of the fibril 

 could be detected whilst it was under the action of the mineral acid. 



The fibrils of the Euplectella Aspergillvmi contain a greater proportion of organic 

 matter, but have, as described in my original memoir, the same siliceous basis as in the 

 present species. In consequence, however, of the different proportion of the glutinous 

 and siliceous principles, they do not behave exactly like the fibrils of Euplectella Cucumer 

 under the tests of heat and acid. In general, when subject to fire, they do not splinter, 

 but merely bend; and when afterwards microscopically examined, show more trace of 

 charring, and sometimes present increased opacity with the appearance of dead or frosted 

 silver. Yet some show clearly their constitution of a siliceous sheath, including fine 

 iridescent filaments or fibrUlules. 



It sometimes happened, in the case of fibrils of the Ewplectella CvM(mer submitted to 

 the acid test, that a small amorphous mass would be adherent to part of a fibril ; and 

 such mass was quickly dissolved with the extrication of abundant gas-bubbles : the 

 inference from this was, that some fragment of a foreign body of carbonate of Hme had 

 become accidentally entangled in the meshwork of the Euplectella. 



In the amorphous portions of sponge to which the Euplectella Cucmner was connected 

 by its long filaments, two modifications of reticulate structure were discovered by Dr. 

 A. Farre. One, represented in PI. XXI. fig. 8, is an irregular network, more or less bent, 

 with subquadrate meshes, sometimes crossed by oblique threads. A second and more 

 beautiful structure is represented in fig. 9. The meshes of this network are on nearly 

 the same plane, and of a more regular square form, with a short pointed spiculum pro- 

 jecting from one side of each decussation of the threads, like the teeth of a harrow. Both 

 figs, 8 & 9 give magnified views of the above structures, with the part magnified of the 

 natural size. Fig. 9 a gives a more magnified view of one of the squares, with its spines, 

 of the ' harrow ' structure. 



To the question put by almost every one to whom the Euplectella is shown, as to how 

 the threads could have been so regularly yet intricately interwoven, I have sometimes 

 replied, that there has been no such thing as interweaving in the case ; that no thread, 

 as such, was ever laid across another in the construction of the Euplectella; that the 

 analogy of human textile fabrics ^oes not apply to this beautiful natural object. In 

 artificial lacework the several stages of a complex result must be taken in the succession 

 indicated by painful and exact calculation : in organic lacework different stages are done 

 at once. Thus it is that the Divine works surpass those of man's utmost ingenuity. 

 The threads of the Euplectella were not first spun and then interwoven, but were formed 

 as interwoven, the two processes going on simultaneously, or 'pari passu.' Just as in 

 the cancellous texture of bone, the plates of bone are not first formed and then fitted to 

 one another, as in building a house of cards ; but the forming and the fitting go on 

 together in the course of molecular gro^v"th. I presume also, that in the beautiful object 

 which we call the Euplectella, we have but its skeleton ; and that, in the living state, 

 the exquisite structiire of the flinty framework may be veiled by the delicate gelatinous 

 enveloping organic tissue. 



VOL. xxn. - B 



