ee 
a toe 
ON PROTOPLASMIC CONTINUITY IN THE FLORIDEX. — 37 
near the middle of the cell, but not always at exactly the same ~ 
vel. 
si i le fastigiata is constructed on a plan which is f 
mentally the same as that of P. ureeolata. The thallus const of. 
a repeatedly bravithed earners sensed throughout of a entr 
a surrounded by a number of ‘ cortical siphons.”’ pasar 
the ends of the central alls coincide with those of the cortical 
ones. Tie mode of branching 1 is, however, dichotomou us, and the 
twen The modifications met with in the different siphon cells 
are As ai we more considerable than any that occur in the 
species just ei ed. 
As regards protoplasmic peers there is ie same primary 
agreement accompanied by secondary difference The proto- 
plasmic bodies of the siphon ecllk are connected lovigitndinally by 
single cords of the same material, which pass through the end 
nt contiguous cells. In the case of the central cells these are 
a 2 ; 
collar, as in the cases previously described. The longitudinal 
connecting threads of the cortical siphons are much finer than 
those of the central one, and are we eranular in appearance. 
There is, however, 6n each of them a collar at eer the mid 
point. These details are represented in in Plate 2438, fig. 
ere again, then, we have a protoplasmic coe en ity in the 
longitudinal direction quite as striking as that of Callithamnion. 
But this is not the only direction in which such a continuity exists, 
for, af in Polysiphonia urceolata, there is a lateral continuity ae 
The peculiar features of this lateral continuity give qui 
oliarnctar to the central eee cells of P. fastigiata, which has sik 
been «ahora in other spec 
na young conditian these cells would seem to be mor 
or less oiindea in shape, and the protoplasm fills up the whole of 
the lumen of the cell. As the cell grows older the wall becomes 
thickened. The thickening, ower | is not uniform, but varies in 
different parts in such a manner that the protoplasm ultimately 
assumes the shape of a teetotum, whose heave is ig or poo 
on the upper and lower surfaces (Plate 243, fig. 5). B ssuming 
this shape the protoplasm of each cell does not hes 5 aliggsthee 
isolated. On the contrary, a number of lateral processes—one for 
each cortical cell — radiate away through the thickening layers 
the cortical cells which surround it, the whole fo Si a Be an inter- 
connected system, whose > etokonlaaiits continuity is roken. 
Ulby. 18 
Plate 248, fig. 5, will afford an idea of the arrangement PaRLET 
- as seen in optical longitudinal section. 
