358 REPORT—18638. 
on the other hand, present the medusoid structure only in a disguised or unde- 
veloped condition. They have the form of sacs, and, except in a single known 
instance, the whole gonophore remains permanently attached to the tropho- 
some, giving rise within it to the generative elements, which, after attaining 
Fig. 3.—Ambulatory medusa of Clavatella prolifera, 
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a certain degree of maturity, are ultimately discharged from its cavity. The 
single exception is afforded by the genus Dicoryne, Allm. (fig. 4), in which, 
before discharging its generative products, the gonophore liberates itself from 
its external investment or ectotheca, and thus becoming free, swims about 
actively by the aid of vibratile cilia. 
Fig. 4.—Free locomotive sporosae of Dicoryne. 
A, Male sporosae, still enclosed in its ectotheca. B and ©, female gonophores after 
liberation from the ectotheca, swimming on the open sea; they represent two views of the 
same gonophore in planes at right angles to one another. 
