IX] OF SO-CALLED MYONEMES 701 



cytoplasm; here we have only to assume that there is a 

 tension at this surface, between the two layers of protoplasm, 

 sufficient to balance the tensions which act directly on the 

 spicule*. 



In various Acanthometridae, besides such typical characteristics 

 as the radial symmetry, the concentric layers of protoplasm, and 

 the capillary surfaces in which the outer vacuolated protoplasm 

 is festooned upon the projecting radii, we have another curious 

 feature. On the surface of the protoplasm where it creeps up the 

 sides of the long radial spicules, we find a number of elongated 

 bodies, forming in each case one or several little groups, and 

 lying neatly arranged in parallel bundles. A Russian naturalist, 

 Schewiakoff, whose views have been accepted in the text-books, 

 tells us that these are muscular structures, serving to raise or 

 lower the conical masses of protoplasm about the radial spicules, 

 which latter serve as so many "tent-poles" or masts, on which the 

 protoplasmic membranes are hoisted up; and the little elongated 

 bodies are dignified with various names, such as "myonemes" or 

 "myophriscs," ,in allusion to their supposed muscular nature f. 

 This explanation is by no means convincing. To begin with, we 

 have precisely similar festoons of protoplasm in a multitude of other 

 cases where the "myonemes" are lacking; from their minute size 

 (0-006-0-012 mm.) and the amount of contraction they are said to 

 be capable of, the myonemes can hardly be very efficient instruments 

 of traction; and further, for them to act (as is alleged) for a specific 

 purpose, namely the "hydrostatic regulation" of the organism 

 giving it power to sink or to swim, would seem to imply a mechanism 

 of action and of coordination not easy to conceive in these minute 

 and simple organisms. The fact is that the whole explanation is 

 unnecessary. Just as the supposed "hauling up" of the proto- 

 plasmic festoons may be at once explained by capillary phenomena, 

 so also (in all probability) may the position and arrangement of 

 the little elongated bodies. Whatever the actual nature of these 

 bodies may be, whether they be truly portions of differentiated 

 protoplasm, or whether they be foreign bodies or spicular structures 

 (as bodies occupying a similar position in other cases undoubtedly 



* Cf. Koltzoff, Zur Frage der Zellgestalt, Anat. Anzeiger, xli, p. 190, 1912. 

 t Mem. de VAcad. des Sci., St Petersbourg, xii, Nr. 10, 1902. 



