THE ORIGIN OF NERVES. 283 



development of the nervous system is made possible through 

 very simple means. Recent experiments conducted by Mr. 

 G. J. Romanes on the Medusida or jelly-fishes, have in a large 

 measure aided our comprehension of the stage in the de- 

 velopment of nerves which follows close upon the primitive 

 condition of the amoeba, and have supplemented by demon- 

 stration the hypothetical influences regarding the origin of 

 nerves which we owe to Mr. Herbert Spencer. 



With the jelly-fishes or Medusidce, few readers can be un- 



FIG. 49. Aiirelia anrita, a common jelly-fish. 



acquainted. They form some of the most familiar as well as 

 most interesting tenants of the sea around our coasts in the 

 summer months. By the aid of a tow-net we may capture the 

 smaller species in hundreds ; many of the so-called medusae, 

 however, being merely the free-swimming and detached 

 reproductive bodies of rooted and fixed zoophytes. The 

 larger species are equally well known to sea-side visitors, in 

 the form of the graceful swimming-bells (Fig. 49) of clear 

 gelatinous matter which pulsate through the calm sea of 

 summer the type of all that is fragile and ethereal in nature. 

 From the middle of the clear azure bell hangs a stalked 

 body, corresponding to the " clapper " or " tongue," and 



