IX] OF THE NASSELLARIAN SKELETON 717 



four cells of a segmenting egg: that is to say with an intervening 

 "polar furrow," whose ends mark the meeting place, at equal angles, 

 of the four cells in groups of three. The Uttle projecting spokes, or 

 spikes, which are set normally to the main basket-work, seem to be 

 uncompleted portions of a larger basket, corresponding to a more 

 numerous aggregation of cells. Similar but more complex forma- 



Fig. 333. An isolated portion of the skeleton of Dityocha. 



tions, all explicable as basket-like frameworks developed around 

 a cluster of cells, and adsorbed or secreted in the grooves common 

 to adjacent cells or bubbles, are found in great variety. 







Kg. 334. Dictyocha stapedia Hkl. 



The Dicfyocha-si^icule, laid down as a siliceous framework in 

 the grooves between a few clustered cells, is too simple and natural 

 to be confined to one group of animals. We have already seen it, 

 as a calcareous spicule, in the holothurian genus Thyone, and we 

 may find it again, in many various forms, in the protozoan group 

 known as the Silicoflagellata*. Nothing can better illustrate the 

 physico-mathematical character of these configurations than their 



* See {iyit. al.) G. Deflandre, Les Silicoflagelles, etc., Bull. Soc. Fr. de Microscopic, 

 I, p. 1, 1932: the figures in which article are mostly drawn from Ehrenberg's 

 Mikrogeologie, 1854. 



