COMPARATIVE ANATOMY. 



279 



beln^ that, a few yean ago, were innooent little children, who, could 

 .-. ivi-<l ,.f Niiuh deed* of darkness, a* they now perpetrato 



wit I. ..i. i , on, p unction, would h.i\. Hhruiik from them instinctively with 



Ttuwo, surely, are prodigious changes, greater far than any exhibited 



. -ifvtuhlo world. And oro they not changes of infinitely greater 



h<> growth of a mMity tree, from a small seed, may bo 



: r ^ .ii.l.-r, for admiruti' m ; luit tho development of a being, 



..{ MIII-II tremendous agencies for good or. for evil, should lx) 



of the deepest concern. Strange, passing trange, 



that it in not BO ! May. 



The next piece is designed aa an exercise in " smooth " and 

 quality " of voice. Tho suavity of tone, which belongs to 

 ii.l tender emotion, should prevail in the reading of this 



beautiful composition. A full, clear, but softened note should 



be heard throughout. 



IX. MEMORY, 

 [pu.t.] "Hs sweet to remember ! I would not forego 



The charm which the past o'er the present con throw 



For all the gay visions that fancy may weave 



In her wel> of illusion, that shines to deceive. 



We know not the future the past we have /alt 



Its cherished enjoyments the bosom can melt; . 



Its raptures anew o'er our pulses may roll, 



When thoughts of the morrow fall cold on tho soul. 



"Tig sweet to remember ! When storms are abroad, 

 We see iu the rainbow, tho promise of God : 

 The day may be darkened, but far in the west, 

 In vermilion and gold, sinks the sun to his rest ; 

 With smiles like the moming he passes away ; 

 Thus the beams of delight on the spirit can play, 

 When in calm reminiscence we gather the flowers, 

 Which love scattered round us in happier hours. 



'Tis sweet to remember ! When friends are unkind, 



When their coldness and carelessness shadow the mind. 



Then, to draw back the veil which envelops a land, 



Where delectable prospects in beauty expand ; 



To smell the green fields, the fresh waters to hear, 



Whose once fairy music enchanted the ear ; 



To drink in the smiles that delighted us then, 



To list the fond voices of childhood again, 



Oh 1 this the sad heart, like a reed that is bruised, 



Binds up, when the banquet of hope is refused. 



'Tis sweet to remember ! And naught can destroy 



The balm- breathing comfort, the glory, the joy, 



Which spring from that fountain, to gladden our way, 



When the changeful and faithless desert or betray. 



I would not forget ! though my thoughts should be dark ; 



O'er the ocean of life, I look back from my bark, 



And see the fair Eden, where once I was blest, 



A type and a promise of heavenly rest. Clark. 



COMPARATIVE ANATOMY VIII. 



ANNELIDA: RINGED WORMS. 



WE have now arrived at a class in the animal kingdom in 

 which the radial symmetry is almost entirely abandoned, and 

 the two-sided arrangement is perfect. In accordance with this 

 advance we find many of these animals gifted with considerable 

 powers of locomotion, and it is in this class that we first find 

 animals which have adopted a quasi-aerial mode of life. Nature, 

 we are told by the ancients, and told truly, does nothing 

 suddenly, and hence, though the arrangement best adapted to 

 rapid locomotion is found in this class, and some of these 

 animals reside in that thin medium through which the body 

 can be impelled with the greatest velocity, yet the means of 

 locomotion in this class are but feeble. The instruments of 

 locomotion, the limbs, are but rudimentary ; and though the 

 earth-worm be capable of breathing in air, it respires on tho 

 aquatic type, and, indeed, requires that its skin bo kept moist 

 to respire at all. Hence, the earth-worm always inhabits moist 

 earth, and makes its peregrinations above the soil after dark, 

 when the sun's rays, which would rapidly dry it up, are directed 

 elsewhere. 



This class also introduces ITS to the articulate type of animals 

 under its simplest form. In the worms the beginnings of all 

 the more complicated organs which we find in the lobster and 

 the bee are present, but present in a very incomplete condition. 

 In accordance with what we have said about the characteristics 

 of an animal of a low grade of structure, we find the vegetative 



repetition of parts here manifested in a high degree. The i 

 parts ate repeated orer and over again, sometimes to the 

 number of many hundreds. In fact, the bodies of these animals 

 may be Mid to consist of a long neries of exactly similar ring* 

 or segments placed one behind the other, and containing all the 

 part* essential to life in each segment. By this statement it is 

 not meant that the animal in an aggregate of individual*, or 

 that it is capable of independent existence if severed from the 

 rest, but merely that the individual in maintained by the inter- 

 dependence of similar parts. In some species this statement 

 is almost literally correct. Thus the earth-worm has a month 

 developed in the under side of the first segment, and an opening 

 in the tail segment for the completion of the alimentary canal; 

 but all the intermediate segment? form a series differing from 

 one another only in size. Each segment has its own ring-like 

 outer wall, its own nervous centre, its compartment of the 

 stomach, its transverse circulatory organs, and its so-called 

 peculiar segmental organs. In some of the water-worms the 

 presence of feelers, proboscises, and jaws in the fore part 

 or of localised gills, etc., in the after parts of the body, some- 

 what interfere with this repetition ; but something corresponding 

 to those organs generally exists in a rudimentary condition in 

 the other segments, and in all the species the parts are inde- 

 finite in number, and many of the segments in each species 

 precisely alike. 



We have said that each segment has its own nervous centre, 

 a centre consisting of two nerve knots, situated on the under 

 side or floor of the segment, and sending lateral nervous- 

 threads to its own special ring. It is, however, essential to 

 individual life that the whole of the nervous system should be 

 united, and therefore, to effect this, two cords run from the two 

 nerve-centres of each segment to each of the adjoining segments 

 before and behind it. This arrangement gives rise to a double 

 beaded or knotted cord of nervous matter stretching along the 

 floor of the body-cavity from end to end. Since the mouth 

 always opens on tho under side of the body, and the organs of 

 sense, when present, ar^ necessarily placed in the neighbourhood 

 of this and in the front of the animal, it follows that the nervous 

 centre, which supplies these organs with nerves (the necessary 

 carriers of sensation), must be situated above the throat, and 

 must also be joined to the next centre lying under the throat by 

 two cords, one of which runs on each side of the gullet ; other- 

 wise symmetry would not be maintained. The form of the 

 nervous system arising from these arrangements is the most 

 distinguishing character of the articulata, and it is retained by 

 all the members of this sub-kingdom, however much they have 

 become modified from tho elongated worm-like type. This 

 character has given rise to the term homogangliata, which 

 means that the animals so named have a system of repeated, 

 similar, nervous knots. This division includes all the articulate 

 animals, and excludes all other animals ; for though the spinal 

 cord of vertebrates may be looked upon by some as the aggrega- 

 tion of a lineal series of nervous centres, yet this tract is not 

 crossed by the alimentary canal in their case, and is probably 

 not homologous with this system at all. 



In this symmetry in the arrangement of the nervous system, 

 and in the segments! condition of their bodies, the worms are 

 like the higher classes of the articulata, which are represented 

 by the centipede insects and crustaceans and spiders. They 

 differ from these in having no definitely jointed limbs, in having 

 a system of blood-vessels completely shut off from the body- 

 oavity whose whole circuit is perfect, and in having ciliated 

 membranes at some period of their lives in some part of their 

 bodies. Besides these distinctive characters there is another 

 vory generally possessed by worms, and that is that the 

 exterior of their bodies, instead of being stiff and hard, is soft 

 and flexible. The body-wall is composed, not of a horny sub- 

 stance called chitine, as is the case in insects ; but of mem- 

 braneous material, in the internal layers of which muscular 

 fibres are embedded. Since there are no jointed levers for 

 limbs, it follows that the whole movement of the body must 

 depend on the flexibility, contractility, and elasticity of the 

 integument, and hence the soft character of the outer integument 

 is a matter of necessity. 



The species which stands as the representative of the whole 

 of this class, both on account of its occurrence everywhere, and 

 of the multitude of individuals which it composes, is the common 

 earth-worm (Lumbricus ttrrioola). Nevertheless, this is rather 



