528 



SCIENCE. 



[N. S. Vol XV. No. 379. 



sion will be greatest at the posterior end 

 and null at the anterior end of the body, 

 with a complete gradation between the two 

 extremes. 



The chains of Stenostoma always taper 

 posteriorly, as would be expected if this 

 tension is effective in modifying form. 



The elongation and decrease in trans- 

 verse diameter of pieces are exactly what 

 might be expected if the tension is effect- 

 ive. 



And, furthermore, it is possible to pre- 

 vent the change of form (morphallaxis) by 

 preventing the animals from attaching 

 themselves. The form change occurs very 

 rapidly in Stenostoma, being complete in , 

 twenty-four hours or less. Pieces were pre- 

 vented from attaching themselves during 

 twelve hours after operation and then were 

 compared with pieces, originally of the 

 same size, which had been allowed to attach 

 themselves. The pieces which had not been 

 allowed to attach themselves were little 

 changed, while the controls had elongated 

 in some cases nearly half of the original 

 length and tapered strongly to the posterior 

 end. 



It was found also that the chains attach 

 themselves more readily to rough than to 

 smooth glass. A little very fine sand on 

 the bottom of a glass vessel is sufficient to 

 cause the animal to attach itself more read- 

 ily and therefore to change its form more 

 rapidly than a specimen kept in a clean 

 glass jar. 



In all these experiments the specimens 

 were kept without food. 



The experiments show that form-regula- 

 tion (morphallaxis) in Stenostoma is, at 

 least in large part, purely a mechanical 

 phenomenon, not the effect of stimuli. 

 Cord and Brain: J. B. Johnston. 



Recent studies upon the brain and cra- 

 nial nerves of lower vertebrates show that 

 the nervous system, exclusive of the sympa- 

 thetic and higher brain centers, falls into 



four chief functional divisions. These are 

 as follows: 



A. Somatic sensory division: Consisting 

 of the free nerve endings and sense organs 

 (neuromasts) in the integument, exclusive 

 of end buds ; nerve components innervating 

 these organs (dorsal roots, exclusive of 

 sympathetic fibers, V., VIII. and lateral 

 line roots) ; and the nerve centers in which 

 these components end (dorsal horn, tuber- 

 culum aeusticum and cerebellum). Its 

 stimuli give rise to reflexes which affect the 

 animal's relations to its environment, and 

 in higher forms commonly give rise to sen- 

 sations and conscious reactions. 



B. Splanchnic sensory division: Free 

 nerve endings in the lining of the alimen- 

 tary canal, sense buds in the branchial and 

 mouth cavities, and on the surface of the 

 head and body (end buds) ; components 

 innervating these (syrapathetic fibers in 

 the dorsal roots, X., IX. and VII. roots), 

 and centers in which these components end 

 (Clarke's column and lobus vagi or fasci- 

 culus communis with its nuclei). Its stim- 

 uli give rise to refiexes which serve the 

 functions of nutrition, respiration, circu- 

 lation, etc. 



C. Somatic motor division: The ventral 

 horn of the cord, the nuclei of the XII., 

 VI., IV. and III. nerves, the somatic motor 

 fasciculus and its 'tween brain nucleus, 

 and the motor components innervating 

 somatic musculature. 



D. Splanchnic motor division: The 

 region of the lateral horn in the cord, the 

 nuclei of the X., IX., VII. and V. cranial 

 nerves; and the motor components inner- 

 vating splanchnic musculature. 



In the parts of the brain rostral to the 

 medulla the splanchnic sensory and motor 

 divisions are wholly lacking, while the 

 somatic motor extends forward nearly to 

 the rostral end of the brain axis and the 

 somatic sensory division includes the cere- 

 bellum and probably the tectum opticum. 



