LUMINOUS ORGANS AND LIGHT OF THE PBNNATUL^. 249 



had the power of giving light in such a way that the finger 

 which touched and pressed these little polypes became covered 

 itself with luminous matter. 



After the historical quotations the memoir is divided into 

 two parts — the one anatomical, in which are given descrip- 

 tions for the first time of the luminous organs of the Penna- 

 tulae ; the other physiological, in which are described all the 

 experiments made in the investigation of the phenomenon of 

 the luminosity. I take advantage of this opportunity to thank 

 publicly Professor Francesco Gasco, who was my assiduous 

 companion in these discoveries. The result of the anatomical 

 researches may be summed up as follows : 



1. In the Pennatulse and similar genera, and apparently in 

 all the phosphorescent Pennatulidse, the light eminates exclu- 

 sively from the polyps and the zooids (rudimentary polyps). 



2. The phosphorescent organs of the Pennatulee consist of 

 eight cords (cordoni luminosi), which adhere to the external 

 surface of the stomach of the polyps and the zooids, and 

 are continued into each of the buccal papillae of both. 



S. These cords are principally composed of a substance 

 contained in vesicles or cells, and which has all the characters 

 of fatty matter, including that it does not decompose imme- 

 diately after the putrefaction of the polyps. To these are 

 added multipolar cells and albuminoid granulations. 



In the Pennatula phosphoria is found besides this a mineral 

 substance, white, granular, and indefinite in its composition, 

 but which is neither a carbonate nor a calcareous phosphate. 

 This matter is wanting in the Pennatula rubra, in the Pte- 

 roides griseum, and in the Funiculina quadrangularis, which 

 present, however, organs and luminous phenomena similar to 

 those of the P. phosphoria ; hence it results that no special 

 importance can be attributed to them. However, it renders 

 the cords of the P. phosphoria very white, and thus permits 

 them to be observed by transparency through the teguments 

 of the little polyps. The softness and fragility of the lumi- 

 nous cords are such as to prevent all minute histological 

 research. It is, then, to the fatty nature of the substance 

 which composes these cords that it is necessary to attribute 

 the fact that the anatomists who have studied the anatomical 

 structure of the Pennatulse from specimens preserved in 

 spirit have not been able to discover these organs. 



However slightly a little polyp may be compressed, the 

 luminous cords soon break, and the photogenic matter is 

 then able to project itself into the cavity of the tentacles, 

 whence it is easy to collect it for observation ; but if the 

 pressure acts in the direction of the Polypidom this same- 



