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tvhich have their edges at first entire, but which afterwards become 
deeply serrated. As the leaflets increase in size they direct them- 
selves vertically from the upper surface of the ramulus, and those of 
one side arch over, so as to approach those of the opposite. They 
are at first free, but they afterwards become intimately united at 
their edges, while those of one side ultimately coalesce with those of 
the other by their summits, and thus form a completely closed re- 
ceptacle. Each leaflet contains a cavity which is only a prolonga- 
tion of that of the ramulus. 
In this receptacle the gonophores are produced. They spring 
from the upper side of the metamorphosed ramulus at the point 
where the leaflet leaves it, and take the place of the polype cells on 
an ordinary ramulus. They begin to be produced at an early stage 
of the corbula, and may be easily examined in the young corbula 
while yet open. 
The metamorphosed ramulus generally remains unchanged for a 
short distance from its origin, and here may be seen bearing one or 
two ordinary polype cells. 
About twelve gonophores are generally contained in each corbula ; 
they are of the simple type, of a regular oviform figure, and are 
invested with a delicate extension of the polypary. The sporosac 
has a well-developed manubrium, which is quite simple, and extends 
nearly from the base of the sac to the summit. I have not found 
more than a single ovum in the female sporosacs I examined. In 
the male sporosacs, the cavity is filled with the spermatogenous 
tissue. 
General Conclusions. 
A comparison of the different forms of gonophore presented by 
the several species just described, and by some others not included in 
the present paper, shows that they are referable to three distinct types. 
1. The simple gonophore, such as we find in Hydractinia, Cor- 
dylophora, &c. 
2. The naked compound gonophore consisting of blastostyle and 
sporasacs, but destitute of investing capsule. Examples of this 
form are found in Tubularia and Clava. 
3. The capsular compound gonophore , consisting of blastostyle 
and sporosacs, and having the whole invested by a distinct capsule. 
This type occurs in Campanularia, Laoiuedea, &c. 
