CONTRACTILITY AND PHOSPHORESCENCE. 183 



who has plainly traced it to the secretion of special glands, yet 

 when we find the same phosphorescence equally as brilliant in 

 eggs of Ctenophorae as in the adults, even in the stages in 

 which the masses of segmentation can still be counted, we have 

 evidently not yet reached the solution of the true nature of this 

 phosphorescence. The whole embryonic mass becomes bril- 

 liantly phosphorescent when the least shock is given to the jar 

 in which the eggs are kept." 



The probable explanation of this remarkable phenomenon is 

 that the mechanical shock given to the jar causes the proto- 

 plasm of the egg to contract, and this contraction is accom- 

 panied by the manifestation of light. The well-known case of 

 phosphorescence of Noctiluca, to which I shall refer in detail 

 later, belongs to the- same category. Any stimulus that causes 

 the contraction of the protoplasm also causes the phosphores- 

 cence of the organism. 



One of the most eminent students of phosphorescence, Qua- 

 trefages, 1 while freely admitting the efficiency of the oxida- 

 tion theory of phosphorescence, sharply draws a line at the 

 last class, where phosphorescence is associated with contrac- 

 tion, and falls back on the vitalistic theory of luminous phe- 

 nomena in vogue at the beginning and in the middle of the 

 present century. But I think it is especially this sort of phos- 

 phorescence which is of peculiar interest to us. Intimately 

 connected as it is with the phenomena of contraction, we may 

 hope that the careful consideration of the subject may throw 

 some light on the understanding of protoplasmic contraction 

 itself. 



Let us examine somewhat in detail the facts of the case, 

 and then consider them in connection with the phenomena of 

 muscular contraction. Noctiluca is a little microscopic animal, 

 sometimes attaining the diameter of i mm., bearing a general 

 resemblance to little melons, deeply indented at one end (Fig. 4). 

 Near this depression there is an appendage by which the ani- 

 mal moves slowly to and fro, swaying it from right to left. 



1 Quatrefages, A. de, " Memoire sur la phosphorescence de quelques inverte- 

 bres marins," Ann. des Set. Nat., 1850, vol. xiv, pp. 236-287; "The Phosphor- 

 escence of the Sea," Popular Science Review, vol. i, 1862, pp. 275298. 



