292 WILSON. [VoL. IX. 
The nuclei are so small that one cannot make much out of 
them. The central chromatin mass is conspicuous and rela- 
tively so large that it is only in exceptional cases that the 
nuclear membrane can be made out. Asa rule, all one can see 
in a section of the mature gemmule, is a number of small 
chromatin masses scattered through a finely granular and 
deeply staining matrix. This veiling of the cellular nature of 
the mature gemmule in Esperella is of importance, it will be 
seen, as explaining the nature of the gemmule in Tedania. 
The young gemmule, as has been said, lies in the mesoderm 
. of a trabecula. It does not project into the canals, and it is 
surrounded by a follicle composed of a single layer of flattened 
cells. Such young gemmules are shown in Pl. XV, Fig. 12, 9”. 
As the gemmule grows it compresses the surrounding tissue, 
and begins to project into one of the adjacent canals. The 
gemmule g’ in Fig. 12 may be taken as illustrating this stage. 
With the increase in growth the gemmule comes eventually to 
lie in the cavity of a canal, the surrounding tissue having been 
gradually compressed into the form of a sheath, which is sus- 
pended from the wall of the canal by strands of tissue. The 
larva Z, and the mature gemmule g, of Fig. 12, illustrate this 
stage. The sheath, sZ., Pl. XV, Fig. 12, and Pl. XVI, Figs. 21; 
22, consists of several layers of flattened cells and is indistin- 
guishably fused with the original follicle, except in rare places 
such as that shown in Fig. 22, where inside the sheath is seen, 
at one end of the gemmule, the original follicle, gf In the case 
of this gemmule, Fig. 22, the compression of the surrounding 
tissue has not involved the mesoderm at one end of the gem- 
mule, and in this region flagellated chambers are still to be 
seen, 
Though the sponge during the summer is filled with gem- 
mules, the asexual breeding season being~ apparently at its 
height, small egg-cells are met with here and there. They are 
not common but can be found after a little search. The egg- 
cells are always quite small and in the midst of a large collec- 
tion of mesoderm cells closely packed, Pl. XV, Fig. 20”, 0. ov. 
As a rule they have not a follicle, and in this condition are 
probably amoeboid — witness the process of the ovum in Fig. 
