362 REPORT—1863. 
lobes, so as to make out with certainty whether they be homologous with proper 
sporosacs. They may ultimately prove so; but until then it will be safer to 
restrict the term “ gonoblastocheme” to those forms to which I have here 
applied it. When it shall be shown that specialized sexual zooids are developed 
from the manubrium, the same term must then be extended to the medusze 
in which this phenomenon can be proved to occur. 
Besides giving origin to their generative elements in special sexual buds 
developed on the radiating canals, the gonoblastocheme differs still further 
from the gonocheme in the almost universal absence of “ ocelli” on the bases 
Fig.5.—Diagrammatic sections of adelocodonic and phanerocodonic gonophore. 
B A 
Til 
A, Adelocodonie gonophore. B, Phanerocodonie gonophore. 
a, ectotheca ; 5, mesotheca or umbrella; c, endotheca; d, spadix; e, ova; f, radiating 
gastrovascular canals ; g, circular gastrovascular canal seen in transyerse section; A, mar- 
ginal tentacle ; 2, ocellus in bulbous base of tentacle ; 4, velum ; 7, peduncle of gonophore; 
m, general cavity of ccenosare ; 7, mouth. 
In both sections the endoderm is distinguished from the ectoderm by giving it a darker 
shade. 
of the tentacles, and the presence of “ lithocysts,”” which are developed on the 
intertentacular spaces of the umbrella margin*. 
C. Homological parallelism between the sporosac and the medusa, and between 
the gonophore and the polypite. 
While it will be found very convenient to insist upon the differences pointed 
out above between the phanerocodonic and the adelocodonic genophores, it must 
* An exceptional condition is presented by Thaumantias as limited by Gegenbaur, and 
by Siabberia, Forbes, in both of which ocelli are present and lithocysts absent, though the 
meduse belong to the type of the gonoblastocheme ; while in Tiaropsis diademata, Agass., 
another medusa of this type, a well-defined pigment-spot has been described by Agassiz 
as existing in the base of the lithocyst, a statement which I can confirm by my own 
observation on an undescribed species of Tiaropsis captured on the Firth of Forth. 
