292 IV/LSOiV. [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. As a 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 PI. XV, Fig. 12, g". 

 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 /, and the mature gemmule^, of Fig. 12, illustrate this 

 stage. The sheath, sh., PI. XV, Fig. 12, and PI. 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, g.f. 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 egiT- 

 cells are always quite small and in the midst of a large collec- 

 tion of mesoderm cells closely packed, PI. 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. 



