Defence among certain Medusce. 343 



other genera of the groups in which they exist. The new 

 metliod of defence is found, as far as known, only amons: 

 the feiphono])liores, and is limited to one or two genera. 



Let us, on the threshold of our study, consider tlie history 

 of the discovery of the structures in which this peculiar power 

 is thought to be lodged. 



In the year 1880, while engaged in the study of an 

 Agahna, found at Villa Franca, South France, I noticed on 

 the covering-scales certain coloured bodies which resembled 

 in distribution in longitudinal rows the nematocysts which 

 are ordinarily found on these structures. In the same year 

 (1880) I described and figured these bodies, and called 

 attention to the fact that when the covering-scale is broken 

 from its connexion with the axis a coloured fluid is emitted 

 from these organs. A covering- scale, ruptured from its con- 

 nexion, was seen to pour out a considerable quantity of yellow 

 fluid and to discolour the water in the immediate vicinity. 

 When irritated, even while the bract is attached, the animal 

 was supposed to discharge the colouring-matter in the same 

 way although not in the same quantity. A similar pheno- 

 nienon^ connected with other organs, had already been 

 described, for a discharge of colouring-matter from the tasters 

 of Forftl^alia had been observed and mentioned by KoUiker ; 

 but, as far as known, no one had spoken of a like power of 

 the chromatic '' cells " or glands of the covering-scales of any 

 Siphonophore. 



My observations were not verified, or, at least, were not 

 mentioned, by those who studied the Mediterranean Physo- 

 phores up to the close of last year, when Dr. M. Bedot * again 

 took up the subject, and from a study of what he regards a 

 new species of Agahna {A. Glausi)^ possibly the same as 

 mine, or, at least, found in the same locality, described and 

 figured these glands again, generously quoting my description 

 of eight years ago. His additions to our knowledge of the 

 subject are so important that I have taken the liberty of 

 quoting from his account somewhat at length. 



Bedot says (p. 79) : — " Ce qui donne un aspect particulier 

 au bouclier, c'est la presence, a sa surface, d'un grand nombre 

 de petites taches d'un rouge-carmin fonce (fig. 13, gl). 

 Lorsqu'une de ces Agalmes est capturee, elle rejette une 

 quantite tr^s considerable de mati^re colorante d'un rouge 

 jaune tr^s intense. Pour I'observer facilement, on est oblige 

 de changer phisieurs fois I'eau du bocal ou elle se trouve. Au 

 premier abord, j'ai cru que cette mati^re colorante provenait 



* 'Tirage a part du Recueil Zoologique,' t. v. fasc. 1. "Sur V Agahna 

 Clausi." 



