280 W. WOODLAND. 
somewhat better than those obtained with picro-carmine, the 
clear elongated “ vacuole ”’ or mould in the substance of the 
apical cell at the extremity of the spicule ray, e.g. being 
made more evident. 
I find it very difficult on any supposition to account for 
the statements and figures of spicule formation supplied by 
Maas. 
APPENDIX B. 
I have provided two additional figures (43 and 44) which 
I think bear out the conclusion, based on 4 priori grounds, 
that some monaxons in these Sycons—presumably the larger 
kind—originate from two mother-cells. If figs. 43 and 44 
be compared with figs. 3 and 5, it will, I think, be admitted 
that there are here presented two distinct modes of origin of 
the monaxon—the bi-division of a single scleroblast and the 
apposition of two being well distinguished by the respective 
cell forms. It may be objected that, as in the triradiates 
and monaxons already described, the original mother-cell 
always divides, the non-division of the two mother-cells of 
the large monaxons would be anomalous. But the objection 
has little weight, for, since “the number of formative cells 
produced from the original mother-cell (or mother-cells) is 
strictly dependent on the maximum size of the spicule 
attained,” it is evident that, if the adult size of the spicule 
does not demand it, i.e. (more logically speaking) if there 
exists no stimulus to division, then the two mother-cells will 
not divide. In cases where division of the mother-cell does 
occur, there is always a good reason for it. Thus, in the 
case of monaxons produced from a single bi-nucleated sclero- 
blast, and in the case of triradiates produced from the 
trefoil, the division of the one or more scleroblasts concerned 
is, under the conditions, a necessity for the production of the 
spicule. And in many Ascons, the huge monaxons possess 
four or more actinoblasts—there exists a stimulus (whatever 
