462 ON CONCRETIONS, SPICULES, ETC. [ch. 



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 characters 

 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 naturaUst, 

 Schewakoff, 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 naturef . This explanation is by no means convincing. 

 To begin with, we have precisely similar festoons of protoplasm 

 ill a multitude of other cases where the "myonemes" are lacking; 

 from their minute size (•006--012 mm.) and the amount of con- 

 traction 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 

 which is difficult to conceive in these minute and simple organisms. 

 The fact is (as it seems to me), that the whole method of explana- 

 tion is unnecessary. Just as the supposed "hauhng up" of the 

 protoplasmic festoons is at once explained by capillary phenomena, 

 so also, in all probability, is the position and arrangement of 

 the little elongated bodies. Whatever the actual nature of these 

 bodies may be, whether they are truly portions of differentiated 

 protoplasm, or whether they are foreign bodies or spicular 

 structures (as bodies occupying a similar position in other cases 

 undoubtedly are), we can explain their situation on the surface 



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

 I Hem. (Ic VAcnd. des Sci., St. Pdlershourg, xii, Nr. 10; 1902. 



