1/j.O HERMANN JORDAN. 



well as its single parts is able to extend completely, therefore 

 without coincident contraction of other muscles. This question 

 was studied with pieces of the musculature, and I found that the 

 extension of the relaxed muscle was performed by means of the 

 pressure of the blood. Under tJie conditions I obsen>ed, the blood 

 had been pressed into lacunae beneath the snail's skin (/. c., PI. 

 II.), and I showed that it was pushed back into the musculature 

 by the extended collaginous tissue, extending it in this way. 

 These lakelets may sometimes be completely "isolated." 



Concerning the waves of locomotion I say, p. 236 : when con- 

 traction takes place, water (" blood ") is driven into the confined 

 part, which thereby is extended ; by this extension tonus is 

 diminished, etc. It will be seen, that I never spoke of " as many 

 isolated bodies of blood being gradually pushed from behind for- 

 wards in the foot as there are areas of relaxation on the sole of 

 the foot." 



Where is the difference between my opinion and that of 

 Carlson ? 



Carlson thinks that every extension is produced by blood 

 and organ -pressure, following the contraction of other muscles. 

 According to my opinion, this mode is assumed in normal loco- 

 motion, while the lakelets produce complete or partial extension. 

 (Perhaps first extension in locomotion also.) Carlson thinks 

 that the special kind of locomotion is nothing else than an exag- 

 gerated normal one, consequently also produced by contraction 

 of the " musculature of the dorsal and lateral walls of the body 

 cavity." * This opinion is wrong because, if this musculature is re- 

 moved, the foot is able to produce normal locomotory waves. 



In conclusion : The opinion Carlson ascribes to me, is in reality 

 not my opinion. My work of 1901 contains all that Carlson 

 publishes as new in 1905, so far as the latter is true. The two 

 modes of locomotion are quite different : in the normal one the 

 blood, which is contained in the lacunae (not in isolated lakelets !) 

 of the foot, extends the musculature ; in the fast one this role 

 is performed by the contents of the body cavity, with the aid of 

 the muscles of the dorsal and lateral sides of the body. 



ZURICH, March, 1905. 



1 This ought to be regarded as the chief result of Carlson's note, because otherwise 

 he would have done nothing to explain normal locomotion. 



