PROTOPLASMIC MOVEMENT. 411 



when that excitation is removed generally take on an elongated, 

 even exceptionally slender, form, fibres, pseudopodia, &c. ; 

 secondly ; resting hyaline protoplasm, as already described, not 

 unfrequently split up completely into exceptionally fine tibrillse ; 

 thirdly, the smallest distinguishable form-elements of other 

 contractile structures (ciliated organs, myophanes, muscle- 

 fibres) have in a resting stage an elongated form. 



The mechanical behaviour of naked protoplasm especially 

 teaches us that the changes of form, particularly the shorten- 

 ing of its contractile elements, must take place with a force 

 which, as a rule, exceeds at any rate the force which the ele- 

 ments, if they were fluid, would put forth in order to assume a 

 spherical form. 



For shortness the hypothetical contractile elements will be 

 called in the sequel' "Inotagmata.'^ In connection with this 

 it must be pointed out that in them the power is generated 

 which causes the contraction, and which has been described as 

 molecular combination (Tagmata, Pfeffer^). Very probably 

 all inotagmata are positive uniaxial doubly-refracting, hence 

 contractility in general appears to be bound up with the exis- 

 tence of positively uniaxial particles.^ 



The active as well as the passive phenomena of protoplasmic 

 movements compel us further to the assumption that the ino- 

 tagmata of the protoplasm are not, like those of muscles and 

 ciliary processes, arranged together in a relatively firm manner, 

 with the axes all in one definite direction, but are, as a rule, 

 fastened together very loosely, and are capable of moving one 

 against the other in all directions, as a natural consequence of 

 which the possibility of the temporary or permanent grouping 

 of a lesser or greater number of inotagmata into definitely- 

 shaped larger masses (fibres, membranes, &c.) is not excluded. 



As a reason for the possibility of alteration of arrangement 

 of the protoplasmic particles, and in connection with the pre- 

 vailing views concerning the molecular structure of organised 

 masses, we must assume the existence of a capability for the 



1 W. Pfeffer, ' Osmotische Uutersuchungen,' p. 32, Leipzig, 1877. 



* " Contractilitat und Doppelbrechung," ' Arch. f. d. ges. Physiol.,' xi, 1875, 



