STUDIES ON BIOLUMINESCENCE. 28 1 



tentacles. No other regions of JEquorea or Mitrocoma phos- 

 phoresce, but at times faint light was to be observed coming 

 from masses (gonads) along the four radial canals of Phialidium. 

 Melicerta is weakly luminous about the manubrium and then 

 only on rather vigorous rubbing between the fingers. 



o Examined with the microscope in the daytime, the margin of 

 the umbrella of sEqiiorea discloses oval masses of yellow tissue 

 corresponding in position with the luminous areas at night. In 

 Mitrocoma, the yellow masses are much closer together forming 

 an almost continuous line in some places. Since the luminous 

 spots observed at night are also very close together in this form, 

 it seems as if the yellow tissue must be luminous tissue. In 

 Cypridina and the worm, Tomopteris, there are also very clearly 

 visible yellow cells in the luminous gland but this is not true of 

 the luminous organ of all forms. These yellow regions of the 

 medusae do not stain with neutral red, intravitam, a fact true 

 also for the yellow cells of Cypridina. In Phialidium or Stomatoca 

 yellow cells cannot be made out but this is possibly because of 

 their small size. 



Examined at night under the microscope, the luminous spots 

 present a beautiful appearance. Under conditions which cause 

 a cytolysis of the cell, such as addition of fresh water or saponin, 

 one can clearly see that the light comes from granules which are 

 rather large and have a definite boundary, light discs. They 

 are not mere points of light. They vary in size and will luminesce 

 for some time, then flash out very brightly and the light intensity 

 slowly fade. Sometimes there is the sudden appearance of a 

 light disk and then gradual fading of the luminescence. In the 

 luminous extract of Cavernularia (2) I have described a similar 

 phenomenon, where, upon addition of fresh water, the light 

 intensity suddenly increases, due to the flashing out of photo- 

 genic granules. Under the microscope the appearance is that of 

 the starry sky. 



By addition of saponin to the luminous tissue, we obtain a very 

 bright light and this is the best method of exciting luminescence 

 for examination with the spectroscope. This discloses a band of 

 light extending from about X = .46 ^ to X = .60 fj.. As far as I 



