STUDIES IN SPICULE FORMATION. 279 
ApprEnpIx A. 
A summary of the statements made by Maas in his account 
of the development of Sycon spicules is here given (from 
‘ Zoological Record’ for 1901, by Minchin). The misleading 
nature of these statements will be rendered most evident by 
appending to them the necessary corrigents. 
(1) Each monaxon arises in a single mother-cell—which is 
not accurately true, since no trace of the spicule occurs until 
the mother-cell has constricted into two portions, each 
possessing a nucleus. 
(2) There is never more than one cell on the smaller 
spicules of this class (monaxon)—whereas, in actuality, there 
are never less than two, however small. 
(3) The large monaxons have numerous formative cells 
upon them, not derived from division of the mother-cell, but 
from the dermal layer de novo—which is demonstrably 
incorrect, the largest monaxons (in Sycon ciliata and 
S. coronata) never possessing more than two formative 
cells, and if, as in some Ascons, they possess four, they are, 
judging by analogy, probably all derived from the original 
mother-cell (or cells). 
(4) The triradiates also arise each in a single mother-cell 
as a concretion, but at a later stage they bear several 
formative cells—a statement which misrepresents the facts 
about as far as it is possible to do, the triradiates being 
derived (as Minchin has described in the case of the Ascons, 
and as is shown above in the case of the Sycons) from three 
mother-cells which have associated together, and built up by 
their six division products. Additional formative cells from 
other sources never occur. 
I may add that I treated several specimens of Sycon 
ciliata with absolute alcohol and ammonium carmine—the 
principal method adopted by Maas; needless to say, the 
results were the same as those obtained by me in my other 
preparations. Indeed, results obtained by this method are 
vou. 49, PART 2,—NEW SERIES, 20 
