540 B. A. MINOHIN. 



be borne iu mind that his "stellate mesodermal cells '' are the 

 same as my " spicule cells." Dendy believes the mesoderm of 

 Calcarea to be packed with stellate connective-tissue cells, for 

 the most part independent of the spicules, and similar in nature 

 to the stellate cells in the jelly of a Medusa; I, on the other 

 hand, have been unable so far to find stellate connective cells 

 of this kind at all in Ascons, and am of opinion that what has 

 been taken for them is the spicule-cells, which in sections 

 are generally found separated from their spicules, as the me- 

 chanical result of section-cutting. Hence Dendy's " stellate 

 cells," being identical with my "spicule-cells," we are agreed 

 in stating that they are " calcoblasts." Where I must differ 

 from Dendy is with regard to the existence of a special mother- 

 cell for the triradiate systems. In the assumption of " primary 

 calcoblasts," of which the existence has certainlv not been 

 demonstrated, we can trace the influence partly of an analogy 

 with siliceous spicules, partly of Metschnikoff's descriptions 

 and figures. 



Dendy considers that " the calcoblasts, at any rate in the 

 case of large spicules, must be amoeboid, for unless they be so 

 I cannot understand how the spicules can increase uniformly 

 in thickness" (1893, p. 225). I have shown, however, that 

 they do not increase uniformly in thickness, but are built up to 

 their full thickness, first at the base and afterwards at the tip. 



The apical ray of the quadriradiate system, according to 

 Dendy, "is not naked, but clothed by an investing sheath of 

 plate-like nucleated cells," which " resemble the cells of the 

 ectoderm" (1891 [2] , p. 14, pi. vi, fig. 2) . Dendy considers these 

 sheaths as mesodermal structures, though "there is nothing 

 to prove that they are not endodermal ;" ^ probably, however, 

 they are "calcoblasts," derived from the stellate connective- 

 tissue cells. The last thing probably with which Dendy would 

 have thought of connecting them is the " yellow granules," as 



1 Bidder, in his review of Dendy's work, regards these cells as endodermal 

 (1891, p. 630), and has some curious remarks on the subject of the mesoderm. 

 This discussion seems to me a proof of how meaningless are the terms "ecto- 

 derm," "endoderm," and " mesoderm," when applied to these forms of life. 



