1 86 BIOLOGICAL LECTURES. 



tractility. He succeeded in seeing the motor muscles of the 

 luminous OpJiiura suddenly illuminated under the microscope. 

 The muscle alone emitted light, the other portions of the foot 

 remaining perfectly obscure. These muscles were not perfectly 

 luminous throughout their entire length, but there appeared 

 disseminated over them a vast number of exceedingly minute, 

 but at the same time remarkably brilliant points, which appeared 

 and vanished with lightning-like rapidity. The outlines which 



FIG. s. Noctiluca miliaris, representing a portion of the body, with a large number 

 of scintillating points. (After Quatrefages.) 



they presented consisted not of an uninterrupted track of light, 

 but of a line formed by a succession of scintillations. 



It would be easy to multiply examples, but the preceding, 

 quoted freely from Quatrefages, will suffice to show some deep- 

 rooted physiological connection between the production of light 

 and the contractility of protoplasm. 



I shall now pass on to the second section of my paper, 

 concerning the nature of protoplasmic contraction ; more par- 

 ticularly the contraction of protoplasm in one of its most differ- 

 entiated aspects the striated muscle cell. 



