ON THE DEVELOPMENT OF LICHENOPORA VERRUCARIA. 101 
?28, the doubt usually arises in consequence of the difficulty of 
distinguishing between z? and z® in the sections. Thus in 
most cases where a fertile zoceclum was marked ?2z?, it was 
certainly z° if it was not 2’. 
Another line in the table refers to cases in which the fertile 
zocecium was either z? or z®, but it was not certain which of 
these two was fertile. 
We thus obtain the result that in the colonies of all ages 
up to Stage G the fertile zocecium was either z? or z> in 
96 cases, while a younger zocecium was fertile in only 6 
cases in which a single embryo was present. The correspond- 
ing numbers for Stages B to D only are 67 and 5. 
Even if a liberal deduction is made from the 96 of the first 
column or the 67 of the second, on the ground of uncertainty 
or possible errors of observation, we are still entitled to con- 
sider that the fertile zocecium which produces the first brood 
of embryos in L. verrucaria is normally one of the two zocecia 
which are first formed by budding after the larva has meta- 
morphosed itself into the primary zocecium of the colony. Two 
of the six cases alluded to in the table as colonies in which 
two zocecia are fertile, have embryos in both z? and z3. In two 
more cases the fertile zocecia were probably z? and z?, In the 
fifth case z?, and in the sixth case z® was fertile in addition to 
a younger zocecium than either of these two. 
The table further brings out the fact that z? is more often 
fertile than z?. An examination of young colonies which have 
been stained and mounted whole, without decalcification, shows 
that z is really older than z’, although there is no evidence of 
this in the later stages. Thus a colony ‘82 mm. long by 
‘15 mm. broad had a mature polypide in z', and a small 
polypide-bud in z*. Another, °35 mm. by ‘24 mm., had poly- 
pides in z! and z?; while a third, -43 mm. by ‘27 mm., was 
developing for the first time a polypide-bud in 2’, in addition 
to having functional polypides in the older zoccia. 
z” is thus clearly older than z’, and we accordingly have the 
following striking result. ‘There is a strong tendency in the 
development of Lichenopora verrucaria for the ovicell to 
