104 SIDNEY F. HARMER. 
Stage A.—Formation of the Definitive Egg. 
Figs. 17 and 18 have already been described in my pre- 
liminary note (8). Fig. 17 represents a colony consisting of 
three fully formed zocecia only. The section is parallel to the 
surface of attachment, in what may be called a horizontal 
plane. The examination of the complete series of sections 
showed that both z! and z? have a brown body, a polypide, and 
a testis. The level of the section figured is not such as to 
show the characteristic orientation of z? (see p. 102); z> has a 
brown body, a polypide, and a conspicuous cell (seen more 
highly magnified in fig. 18), which obviously resembles an 
egg. A few nuclei to the right of the egg probably represent 
the commencement of the investments of the embryo. Sper- 
matozoa were found floating freely in the body-cavity of z! and 
z’, but none were found in the fertile zocecium in this parti- 
cular case. 
I have not observed the process of fertilisation: with any 
degree of certainty, but I believe that it must occur at about 
this stage. The fertile zooecium may or may not have a testis, 
while testes are commonly present in other zocecia, particularly 
during the early stages of embryonic development. In some 
cases, and particularly in old colonies in which new broods of 
embryos are developing, the testes are enormous, being some- 
times as much as *30 mm. long. It can hardly be doubted 
from these facts that fertilisation does occur at some period. 
Considerable masses of ripe spermatozoa are found in the body- 
cavity of many of the zocecia; and it is probable that they pass 
thence, in some way, to the fertile zocecium. The young sper- 
matozoa are always in groups of four, as in Crisia (6). 
The correct identification of the large cell shown in fig. 18 
is clearly of the first importance, and I have thought it 
desirable to figure two other cases of the same kind (figs. 15 
and 16). 
Fig. 15 shows an egg attached toa polypide-bud. z!, z?, and 
z° contained polypides, but none of the other zocecia were old 
enough to possess more than buds. The egg seems to belong 
