104 Amos W. Peters. 



quence in the following work. The abundance ot the material 

 made it possible to select animals of the same large size for most 

 of the experiments. Lots of from four to eight were placed in 

 glass or porcelain dishes containing about one liter of sea-water 

 brought in with the animals. In these dishes most of the tests 

 for phosphorescence were made. 



Several methods of mechanical stimulation, to be used in testing 

 the animals for phosphorescence, were tried and compared. The 

 most efficient of these was stirring the ctenophores by means of a 

 glass rod. Simple contact with the rod frequently succeeded in 

 bringing forth the response of phosphorescence when jarring, 

 shaking, etc., failed. The adult animals being of sufficient size 

 and weight, the contact of the glass rod with them was easily 

 perceptible through the skin and muscles of the experimenter in 

 the dark. This method of stimulation was uniformly adopted as 

 a standard in this work, being also used for small parts of animals, 

 embryos, and eggs. Unless a statement to the contrary is made, 

 a fresh, previously unused lot of ctenophores was used in each 

 test. 



Strict uniformity of conditions and the constant presence of 

 control animals excluded from the observations here recorded, 

 it is hoped, errors arising from insufficient adjustment of the 

 eye as well as from other sources. That these experiments 

 could profitably be repeated and extended with a much greater 

 degree of refinement, is a point the writer desires to emphasize. 



He wishes to express here his indebtedness to Dr. G. H. Parker, 

 of Harvard University, for critical advice and suggestion, and for 

 the revision of the manuscript. He is also under obligation to the 

 Humboldt Fund of the Museum of Comparative Zoology at 

 Harvard College for financial assistance. Furthermore, his 

 thanks are due to the authorities of the United States Fish Com- 

 mission for the use of its laboratory at Wood's Hole, Mass., 

 during the summers of 1902 and 1903. 



II. LOCALIZATION OF PHOSPHORESCENCE. 



I. In Mature Animals. 



As is well known, ctenophores brought into the laboratory 

 disintegrate quite readily. The dead substance of such animals 

 was frequently tested both in the dark-box and in the dark-room. 



