THE NEUROMUSCULAR STRUCTURE 81 



the musculature of that layer. Although the Hertwigs 

 believed that the nervous sublayer was rather uniformly 

 developed all over the actinian, they maintained that a 

 specially rich nervous region was to be found in the ecto- 

 derm of the oral disc, where the beginning of a central 

 nervous organ might be said to occur. This view that 

 the actinian possessed an oral concentration of nervous 

 tissue was accepted by Wolff (1904), and by Groselj (1909), 

 who, however, placed the concentration in the wall of the 

 oesophagus rather than in the oral disc. 



Havet (1901), who studied the nervous system of the 

 sea-anemone Metridium by means of the Golgi method, 

 was unable to confirm the statement that the nervous ele- 

 ments were more abundant in the neighborhood of the 

 mouth than elsewhere and declared that their arrange- 

 ment was such as to justify the expression diffuse rather 

 than centralized. Havet not only claimed a diffuse nerv- 

 ous system for actinians, but he maintained that there 

 were grounds for changing in certain important particu- 

 lars the scheme of nervous interaction proposed by the 

 Hertwigs. According to Havet the so-called ganglion 

 cells described by these authors are really motor nerve 

 cells which receive impulses from the sensory cells and 

 transmit them to the muscles. Thus the elements in the 

 neuromuscular organization of an actinian form a se- 

 quence that reproduces in miniature that seen in the cen- 

 tral nervous organs of the higher animals. Here, as, for 

 instance, in the vertebrate spinal cord, a sensory neurone 

 connects with a motor neurone which in turn leads to 

 a muscle. The reflex arc thus outlined is reproduced in 

 the actinian in that its sensory cell corresponds to the 

 sensory neurone of the vertebrate and its motor nerve 

 cell to the motor neurone. Thus the actinian and verte- 

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