108 On a new kind of Phosphorescence observed 



From the facts we have narrated, it follows, that in certain annelides, 

 the motor muscles of the feet are the sole seat of the phosphorescence. 

 The light which issues from these parts is confined to a completely shut 

 cavit}'-, surrounded with a liquid, in which are completely enveloped 

 the parts endowed with functions perfectly determined, and in which 

 there is no room to suspect the presence of anj'- secretory organ what- 

 ever. Its appearance alwaj's coincides with the contraction of the part, 

 and disappears when this does. From these facts we think we may 

 conclude, that in these animals there is the production of light in the 

 form of sparks, independent of all secretion of other matter. This phe- 

 nomenon, therefore, in no respect resembles what is observed in those 

 insects which are possessed of a distinct luminous organ, which appears 

 almost formed of a net-work of minute air-cells, — in which the light is 

 remarkably enduring, — in which the phosphorescent matter may be col- 

 lected after the animal's death, maintaining its peculiar properties after 

 it has been isolated. No more does the phosphorescence of the annelides 

 resemble that of the Pholades, or of the Medusae, &c., since, in these 

 animals, it depends upon the presence of a mucus which can be collected 

 in considerable quantities. 



These observations respecting the annelides are equally applicable to 

 the ophiuridaj. In fact the arms of these latter are composed of minute 

 calcareous portions, articulated severally to the extremities of each 

 other, as in the vertebra) of the tail of the lizard. The living matter with 

 which they are covered is not merely a homogeneous substance — a kind 

 of animal pulp, as some authors have conceived : different tegumentary 

 layers are readily distinguished in it, and the more solid portions are 

 conjoined by true muscular fasciculte, whose fibres may be perceived by 

 the microscope. It is upon these points alone that the phosphorescence 

 appears : there it exhibits itself under the form of scintillations, — the 

 strise which it appears to form having the same direction with the 

 fibres ; and it does not manifest itself, except when the arm is in mo- 

 tion : As soon as the animal is in a state of repose, no trace of it can be 

 seen, even although the same portions be irritated. Hence, we conceive 

 we may conclude, that in them, as in the annelides, the light is pro- 

 duced in muscular parts, only during their contraction, irrespective of 

 the contact of air, and independent of all secretion, properly so called. 



The manner in which the light is distributed upon the muscles of the 

 annelides appears worthy of remark. I have stated above that it sel- 

 dom occupies the whole of their extent, but appears only, sometimes at 

 the extremities — sometimes in the middle — and sometimes at isolated 

 points. These facts appear completely to agree with what I have else- 

 where stated concerning the contraction of the muscular fibres, which 

 I have observed in the Edvvardsia and the Synaptes. It may be re- 

 membered by some, that I have elsewhere demonstrated that the light 

 scarcely ever occupies the whole length of one of these fibres ; and in 

 tlieir case, I can readily judge, by the minute transverse strise which 



