198 THE ELEMENTARY NERVOUS SYSTEM 



muscles about the same array of types as are found in the 

 sea-anemones. Some muscles, like the circular muscle of 

 the stalk, are apparently quite without nervous connec- 

 tions and respond to direct stimulation; others, like the 

 circular muscle of the proboscis, probably respond as a 

 general rule to direct stimulation, though they may be 

 influenced by nervous impulses ; and finally muscles, like 

 the longitudinal muscle of the stalk, are completely under 

 nervous domination. Some of these, such as the longi- 

 tudinal muscle of the proboscis, exhibit responses that 

 are called forth in such a way that they are indistinguish- 

 able from a reflex in the higher animals. From this stand- 

 point Corymorplia reproduces in miniature all the con- 

 ditions found in the sea-anemones, and this is further em- 

 phasized by the lack of any general nervous center and 

 the consequent great independence of all organs from the 

 side of their neuromuscular activity. Corymorplia, 

 therefore, does not seem to fill the gap between the ex- 

 tremely simple effector system of sponges and the re- 

 ceptor-effector systems of the coelenterates, but rather 

 presents a reduced though not simplified state of the type 

 in the sea-anemone. If the muscles of Corymorplia were 

 more commonly open to direct stimulation than they are 

 and if its activities presented less than can be inter- 

 preted in the nature of a reflex, it might supply more 

 nearly the requisites of an intermediate type, but, as it is, 

 it resembles rather a reduced actinian than a form in any 

 sense intermediate between sponges and sea-anemones 

 (Parker, 1917 e). 



