8 



HARDWICKE'S SCIENCE-GO S SIP. 



modern chemistry has advanced her frontier farthest, 

 and effected her greatest conquests in the investiga- 

 tion of the constitution of matter. 



As I have already indicated, the particular series 

 of this group of substances to which I have 

 to direct attention in connection with pleo- 

 morphism, consists of those fats— such as mar- 

 garine, palraatine, and stearine— which, when de- 

 composed by an alkali, yield an acid of the series 

 in question, and glycerine. It is a very remarkable 

 fact that there are many glycerine compounds of 

 fatty acids which consist of carbon, hydrogen, and 

 oxygen; but, so far as I know, it is only those the 

 acid of which belongs to the particular type (CnH 2 ) n 

 Oo that have the capacity of assuming different 

 physical conditions; thus oleine, which is perhaps 

 a constant accompaniment of stearine, palmatine, 

 &c, in nature, and which differs in composition very 

 little indeed from the type of these bodies, appears 

 to be destitute of the capacity of assuming the allo- 

 typic conditions which are known to belong to 

 those bodies. I have here specimens of these dif- 

 ferent substances— stearine, palmatine, margarine, 

 and oleine ; but it will be sufficient for our purpose 

 to describe the phenomenon in question as mani- 

 fested by stearine. Now stearine in the purest 

 condition in which it has been prepared is at ordi- 

 nary temperatures a solid substance, which, when 

 heated to 125|° E. melts, and then, if kept at that 

 or a slightly higher temperature, resolidifies; after 

 this resolidification it melts only when the tem- 

 perature is raised to 147°, and now solidifies again 

 at a temperature slightly above this melting-point ; 

 but after this last solidification it melts only when 

 the temperature rises to 157°. After this melting, 

 however, it refuses to solidify at any temperature 

 higher than the melting-point we began with — 

 viz. 125f°. In other words, it has three different 

 points of fusion : it melts at the temperature of the 

 first, — solidifies : melts at the temperature of the 

 second, — solidifies ; melts at the temperature of the 

 third, and then solidifies only when the temperature 

 falls below all three points of fusion ; and, after 

 solidifying here it may be made to melt again at 

 the first, at the second, and at the third melting- 

 points respectively, solidifying, as before below all 

 three; and these changes are reproducible in this 

 order of succession to any extent without the 

 slightest loss or gain of weight. Are we to say that 

 these different melting-points belong to one and the 

 same substance, or to three different substances ? 

 Undoubtedly they belong to one and the same sub. 

 stance, but to three different modifications of it. 

 These modifications differ from one another, not 

 only in melting-point, but in several other respects : 

 —the first modification, or that which is formed 

 when the substance solidifies at the lowest of the 

 three melting-points, is amorphous, — it is destitute 

 of all structure whatever; the third is crystalline in 



structure, and is, in fact, identical in all respects 

 with the crystals deposited from a solution of 

 stearine in ether : the properties of the second 

 modification are intermediate between those of the 

 other two. They are distinguishable, also, by their 

 density, as may be seen by those specimens of the 

 first modification floating, while the other two 

 sink in water. What I have said of this pheno- 

 menon as manifested by stearine, holds good of it, 

 with very slight modification, in the case of each of 

 the other analogous substances, palmatine, marga- 

 rine, &c. 



(To be continued?) 



ON A PARASITIC WORM INFESTING A 

 MARINE FISH. 



IN April, 1874, my friend Mr. W. R. Hughes, 

 F.L.S., sent me a fine specimen of the smaller 

 Wrasses, the Crenilabrus rupestris, or " Golds- 

 wing," which had been kept in his marine tank in 

 company with several others. It had fed well and 

 thrived in confinement (its food consisting of smelt 

 and other white-fleshed fish), until about a week 

 before it died, when it showed an inability to keep 

 in the horizontal posture, and died apparently ex- 

 hausted. I received it the next day, witli a note 

 from Mr. Hughes giving the above particulars, and 

 asking for a post-mortem examination, which was 

 made at once, with the following results. 



External appearances. — There was a fulness about 

 the ventral surface which made me suppose that 

 the fish died consequent upon its inability to deposit 

 spawn ; but, as the examination showed, this idea was 

 erroneous, as the fish was an adult male. Mr. 

 Hughes told me the next dajtthat he had held the 

 same opinion whilst the fish was. moribund, and had 

 sent it to me for confirmation. An appearance of 

 inflammation was observed extending upwards and 

 around the anal orifice, but no other external indi- 

 cations of the cause of death were noticeable. The 

 mouth, tongue, eyes, fins, and scales were healthy. 



Internal appearances. — The viscera were all nor- 

 mal in their position, and apparently healthy. The 

 red streak seen on external examination as extend- 

 ing inwards from and around the anal orifice, was 

 evidently due to post-mortem changes. The heart 

 and great blood-vessels, gills, oesophagus, stomach, 

 liver, woolfian bodies, spleen, mesentery, lower ali- 

 mentary canal, and air-bladder, were apparently 

 healthy. Post-mortem staining was evident in 

 nearly all these organs. The brain was well-devel- 

 oped and healthy, with but little change or staining. 

 There was apparently nothiug to be seen by the 

 unaided eye which would account for death. Whilst 

 turning them over with the point of a narrow- 

 bladed scalpel, I discovered a movement amongst 

 the fibres of the connective tissue, which holds the 

 organs in position. With a watchmaker's eye-lens 



