Tllii I'AiiMEiVb MAGAZINE. 



337 



iet meaay that this diagram shows disacctious of the eutozoon, 

 more particularly with regard to ita nutritive and generative 

 system. You see that the suckiug diac to which I before 

 directed your atteutiou, ia in reality a true mouth with which 

 the creature takea in the bile with which it ia aurrounded ia the 

 biliary ducta ; and that this bile passes down through a system 

 of vessels which are ia reality assimilative vessels, and con- 

 sequeatly may be regarded as nutrivive. You observe there 

 ii a peculiarity with regard to this nutritive system. We 

 see an entrauce for the material by which the Ufa of the crea- 

 ture is maintained ; but we see no excretory organ — we ca-nnot 

 perceive that any feculent matter ia thrown out as such from 

 the hinder part or the sides. Strictly speaking, then, this is 

 really au orgau by which the creature receivos into its system 

 that which it requires for its growth, and by which it also 

 rejects from its system that which ia not needed. And here 

 let me- say, that although there are many works upoa the 

 anatomy of the fluke, containiug very nice drawings or en- 

 gravings; though Profeaaor Oweu gives an engraving of the 

 creature in this work on the Invertebrata, and Kymer Jones 

 another in his work on the animal kingdom — iu short, though 

 tiiere are fifty or more representations by as many individuals, 

 there ia really none that can be depended on as being perfectly 

 correct. I say it advisedlj', because I have been engaged ia in- 

 vestigations with regard to the anatomy and natural history of 

 this creature for eight or nine years, taking up the subject from 

 time to time, and working at it occasionally for days together ; 

 and it is only very recently that I have been enabled to satisfy 

 myself as to some intricate points of its structure. I have seen 

 these auimals, when taken fresh from a slaiu sheep, and placed 

 in warm water, eject the biliary matter again and again from 

 the oral opening, which thus, as I have said, performs the 

 office of aa excretory organ as well as being the one by which 

 the creature receives its nourishment ; and the nutritive system 

 has really nothing whatever to do with the generative system. 

 The great point of interest, however, is the system of genera- 

 tion, which, when we corae to examine it, we find to be ex- 

 ceedingly complicated, the tv/o sexes being blended together 

 ia one individual, as we find iu many other creatures. It is not 

 to be considered as au hermaphrodite— that term ia not strictly 

 applicable to it— but it is a biaexile, the two sexes being 

 distinct separate, and perfect. In whatever animal you meet 

 with these entozoa, they are precisely alike in this respect. 

 We have here a representation of the generative system, from 

 which we find that the male organs arc contained in the centre 

 of the body, and that the female organs have their origin at the 

 periphery, uniting iu duets which meet iu the middle, where the 

 true uterus or womb is located, and which is here represented 

 as being filled with a great number of eggs. And after theee are 

 perfected they escape from an opening which is very near in- 

 deed to the central sucking disc. With regard to an appendage 

 near this, aud which is sometimes protruded, and sometimes 

 retracted into the body, it has been supposed to be an intro- 

 raittent organ or penis, and its exiatencr; in all these creatures 

 would rather seem to show thut although they are bi-sexile 

 it is not improbable that copulation takes place between 

 them. We know of a similar instance with regard to snails, 

 which are bi-sexile, and it is well known that they are 

 furnished with an intromitteut organ aa well as a vagina, and 

 that the intromitteut organ of the one extends into the vagina 

 of the other ; and I say it i? not improbable that this takes 

 place with regard to the fluke, but this point is not at present 

 known. The sucking disc, as it is called, which is seen on 

 the ventral part ol the animal, is simply an organ which evi- 

 dently performs the office of holding the creature on when it 

 is traversing the biliary ducts, forming a kind of focal point 

 whence it can travel and iasinuate itself into the minute rami- 

 fications of the ducts. Nor is it improbable, if copulatioa does 

 take place betweeu two of them, that these two suckiug discs 

 approximate to each other for the purpose of contact during 

 tuat period. If you take any fully-developed fluke it would be 

 perfectly impossible for any one to say what number of ova 

 such a creature contains ; but there is one circumstance 

 especially which renders the ova interesting to us, namely, 

 that if we examine them never so carefully, and any number 

 we please, those that have been naturally expelled from the 

 creatures as well as those that are contained within them, we 

 shall find that there never exists within the ovum anything of 

 the outline of the young fluke ; and this fact being establilshed, 

 it ia evident that in order for the fluke egg to produce ulti- 



mately a fluke, the germs contained withiu it must pass 

 through a aeries of traiismutations— that either metamorphoses, 

 as they have been called, or alteraationa of generations, must 

 talie place ; and it is by studying these that we can get at 

 something like valuable iuformation with reference to the man- 

 ner iu wliich these creatures are propagated. It is now several 

 years siuce I thoroughly convinced myself of this fact, and I 

 believe nearly every person who is at all observing or (amiliar 

 with t'ne circumstunce knows that if you slit up the gall ducts 

 of sheep or any other auimals long <> fleeted with distoma, though 

 you may see iiome of these creatures smaller than others, you 

 never see what might be called a number of young flakes ; nor 

 will you be able to discover a young fluke by microscopically 

 examining the bile iu which they live. This, then, together 

 with the other circumstance to which I have referred, shows 

 at ouce there ia not a reproduction of these entczoa within the 

 biliary ducts ; so that (to put it in a practical way) supposing 

 a sheep to receive six of these flukes into the biliary ducts, 

 they would never multiply therein. They would deposit mil- 

 lions of Ctigs in the smallest ramifications of the ducts — instinc- 

 tively deposited there, it would acem, for the purpose of pre- 

 venting them from too rapidly flowing out by the contractile 

 fuuctioua of those ducts — but you would never have more than 

 six flukes. Now, what does this explain ? It explains a fact of 

 every day occurrence. A person will often tell you, "I sent a 

 lot of sheep to the butcher : I never had more perfect or beau- 

 tiful animals : they were as fat as sheep could be ; yet the 

 butcher found eight or niae or ten or twelve flukes in the liver." 

 The fact is that here they did not exist in suflicient numbers 

 to lay the foundation for disease. If it were otherwise we can 

 see that if one fluke only passed into the biliary duct it would 

 multiply almost ad injlniltim, and the animal must ultimately 

 fall a victim to the alfectiou induced thereby. Here then we 

 have a practical result at once, arising with many others from 

 au investigation of the natural history of this creature. 

 I have said that it must pass through a series of metamor- 

 phoses, or what have been designated alternations of gene- 

 rations ; and perhaps I may be allowed to explain the dift'e- 

 reuce made by scientific men between the two. In alternations 

 of geueraticns we have an aaiu:al which bears a young one as 

 an ovum ;, the young, however, which come from the ova are 

 dissimilar altogether from their parent, but are nevertheless 

 capable of a new system of generation, and the youug which 

 thej' propagate as a second or a third step, pass back to the 

 original form. Ordinary metamorphosia is a different thing. 

 Take the case of a bed-tlea for example, that being the first 

 that occurs to me. The auimal produces ova ; these ova pro- 

 duce larvso ; the generative system becomes developed, but 

 the larva docs not propagate : it attains its full size, and then 

 becomes a chrysalis or pupa ; subsequently the perfeci flea is 

 formed out of the chrysalis, and it is in that state that the 

 generative system reaches its highest order of development. 

 There is no alternation of generation, in other words there is 

 no generation from the larva or pupa. Now this is a part of 

 the natural history of the fluke, which, although it has re- 

 ceived the greatest amount of attention from iavestigators on 

 the continent and in England for some time past, is still to 

 a considerable extent shrouded iu mystery. We have satis- 

 fied ourselves, as I have before explained to you, that we have 

 from out of fluke eggs living creatures exceedingly small, 

 much smaller than the egg itself, and that these do not 

 immediately pars into flukes, but go through a series of 

 alternations of generations. Now what I am going to explain 

 will only allow of an analogy with regard to these creatures. 

 Before explaining it, however, let me say that we believe that 

 each of these fluke eggs, which you see represented ia the 

 diagram, contains a number of moving ciliated cells, which are 

 more or less round in form ; that these, passing into water 

 for example, when the operculum comes off, are net at liberty ; 

 that they become parasitic to some of the creatures which are 

 met with in water, aud that when so parasitic they have the 

 capability of propagating themselves ; that they subsequently 

 pass through a series of changes, and again become, as I shall 

 show you by aualogj', parasitic a second time to other crea- 

 tures when they change into the fluke-like form. So that 

 tracing the process all through we may say that the egg sent 

 forth a circular germ which was ciliated, and which had a rota- 

 t' ry motion in water; that ia this condition it becomes parasitic 

 probably to molluscs, small snails, and things of that descrip- 

 tion ; that when it gets into the body of these creatures, work- 



