BfrtiniTitry nf ^Trn'mntrrj Jtature. 639 



no torture has ever elicited from them an 

 intimation of suffering ; tliey have l>een 

 pinched with forceps, lacerated in all direc- 

 tions, bored with hot irons, and attacked 

 with the most energetic chemical stimuli, 

 without shrinking or exhibiting the remotest 

 appearance of sensibility. On the other 

 hand, in the vegetable world we have plants 

 which apparently feel in this sense of the 

 word. The sensitive plant, for example, 

 which droops its leaves upon the slightest 

 touch, would have far greater claims to be 

 considered as being an animal than the 

 sponges, of which we are speaking." 



\Ve have thought proper to introduce the 

 foregoing quotation, there being no point of 

 dispute in natural history which has been 

 more often or more fiercely contested than 

 the true nature of sponges. That the animal 

 and vegetable organizations both terminate 

 obscurely toward the inorganic structures of 

 creation, and that in this approach to their 

 common boundary they touch and melt into 

 each other at more than one point, must be 

 evident to all who have given the subject 

 the slightest consideration ; and it cannot 

 be wondered at that in this instance, where 

 the lines of demarcation are so indistinct, 

 different reasoners have come to different 

 conclusions. Thus we find Dr. Johnston, 

 who omits them in his work on British Zoo- 

 phyta, asserting that they have no animal 

 structure or individual organs, and exhibit 

 no one function usually supposed to be cha- 

 racteristic of the animal kingdom. " Jake 

 vegetables," he says, " they are permanently 

 fixed ; like vegetables, they are non-irri- 

 table ; their movements, like those of vege- 

 tables, are extrinsical and involuntary ; their 

 nutriment is elaborated in no appropriated 

 digestive sac ; and, like cryptogamoua vege- 

 tables or algte, they usually grow and ramify 

 in forms determined by local circumstances, 

 and if they present some peculiarities in the 

 mode of the imbibition of their food, and in 

 their secretions, yet even in these they evince 

 a nearer affinity to plants than to any ani- 

 mal whatever." 



We all know that the common Sponge is 

 made up of horny, elastic fibres of great 

 delicacy, united with each other in every 

 possible direction, so as to form innume- 

 rable canals, which traverse its substance in 

 all directions ; and to this structure it owes 

 its useful properties, the resiliency of the 

 fibres composing it making them, after com- 

 pression, return to their former state. But 

 it is principally to the observations of Dr. 

 Grant (which have been confirmed by other 

 naturalists) that we owe the elucidation of 

 the real character of the spongy structure, 

 and of its vital action. The dried sponge is 

 only the skeleton of the living animal : in 

 its original state, before it was withdrawn 

 from its native element, every filament of 

 its substance was coated over with a thin 

 film of glairy semifluid matter, composed of 

 aggregated transparent globules, which was 

 the living part of the sponge, secreting, as it 

 extended itself, the horny fibres which are 

 imbedded in it. When Sponges are ex- 

 amined in their living state and natural 

 condition, a constant and rapid stream of 



water is seen to issue from the larger orifices 

 or vents. This stream is made apparent by 

 the movement of the minute particles con- 

 tained in it, and by the disturbance of those 

 which may be floating in the surrounding 

 fluid. On the other hand, it is easily made 

 apparent that water is as constantly being 

 imbibed through the minute pores ; and 

 that, after traversing the smaller cavities of 

 the spongy structure, it finds its way into 

 the canals through which it is expelled. No 

 cause has been assigned for this movement, 

 nor is it easy to assign any : no cilia have 

 been discovered ; and the tissues are pos- 

 sessed of so little contractility, that it is 

 difficult to suppose the fluid propelled 

 through the tubes by any mechanical influ- 

 ence on their part. That the nutrition and 

 growth of the Sponges depend on the water 

 which enters the pores, and on the minute 

 substances it holds in solution, appears evi- 

 dent. And not only does this circulation of 

 fluid answer the purposes of nutrition, but it 

 is subservient also to the process of excre- 

 tion. On watching the currents of water 

 that issue from the vents, it is observed that 

 minute flocculent particles are incessantly 

 detached and carried out by them. " The 

 growth of the Sponge is thus provided for ; 

 the living gelatinous matter continually ac- 

 cumulates, and, as it spreads in every direc- 

 tion, secretes and deposits, in the form pecu- 

 liar to its species, the fibrous material and 

 earthy spicula which characterize the ske- 

 leton." From this description of the struc- 

 ture of a Sponge it will be apparent that all 

 parts of the mass are similarly organized i 

 a necessary consequence will be, that each 

 part is able to carry on, independently of 

 the rest, those functions needful for exist- 

 ence. If, therefore, a Sponge be mechani- 

 cally divided into several pieces, every por- 

 tion becomes a distinct animal. 



" The multiplication of Sponges, however," 

 as is observed by the author before quoted, 

 and to whose able work we again refer, " is 

 effected in another manner, which is the 

 ordinary mode of their reproduction, and 

 forms a very interesting portion of their 

 history. At certain seasons of the year, if a 

 living Sponge be cut to pieces, the channels 

 in its interior are found to have their walls 

 studded with yellowish gelatinous granules, 

 developed in the living parenchyma which 

 lines them ; these granules are the germs or 

 gemmules from which a future race will 

 spring ; they seem to be formed indifferently 

 in all parts of the mass, sprouting as it were 

 from the albuminous crust which coats the 

 skeleton, without the appearance of any 

 organs appropriated to their development. ! 

 As they increase in size, they are found to 

 project more and more into the canals which 

 ramify through the Sponge, and to be pro- \ 

 vided with an apparatus of locomotion of a ! 

 description which we shall frequently have ! 

 occasion to mention. The gemmule assumes j 

 an ovoid form, and a large portion of its 

 surface becomes covered with innumerable 

 vibrating hairs or cilia, as they are denomi- 

 nated, which are of inconceivable minute- 

 ness, yet individually capable of exercising 

 rapid movements, which produce currents 



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