116 SIDNEY F. HARMER. 
wall which is invaginated at the orifice of the zoecium. The 
colony is larger than the preceding specimen, measuring 69 mm. 
by ‘51 mm., and possessing at least twelve brown bodies. The 
fertile zocecium is here neither z? nor z’, but a younger indivi- 
dual of the colony. The figure shows that the suspensor and 
the follicle are still easily recognised. The brown body has, 
however, acquired a much more definite capsule of cells than it 
had in the previous stage. This capsule is not so fully formed 
in the somewhat earlier condition shown in fig. 28; but in 
fig. 27 it has become extremely definite. Its protoplasm and 
its numerous nuclei take up hematoxylin with an avidity that 
shows that the tissue is actively growing, and it is indeed this 
tissue which appears to be, somewhat later, closely concerned 
with the development of the trumpet-shaped aperture of the 
ovicell. The embryo is distinctly larger than it was in Stage C. 
Fig. 26 represents the embryo of another colony (in Stage D), 
which was slightly younger than that from which fig. 28 was 
taken, as it had only five brown bodies and four polypides ; z? 
was fertile. The embryo in this case possesses a peripheral 
layer of nuclei, which surround a central group of three nuclei. 
I am unable to say whether there is any morphological differ- 
ence between the central group and the others. 
It might be supposed, a priori, that Stage D originates by 
the degeneration of the fertile polypide in Stage C. I have 
distinct evidence that this is the case. The polypide is seen to 
begin to degenerate, and the brown body already present 
begins to become confluent with it. The old brown body and 
the degenerating polypide become surrounded by a common 
capsule of cells. The fertile brown body of Stage D hence 
differs from that of Stage C, inasmuch as it contains the 
remains of what was the fertile polypide in the earlier stage, 
in addition to the original brown body. Should development 
proceed normally, no further polypide is developed in the 
fertile zocecium, and the brown body moves to its upper 
end, and eventually comes into close relation with what was 
formerly its orifice. 
The size of the colony during Stage D is in most cases from 
