360 WILSON. [Vot. IX. 
In young Stellettas (Sollas 28, pp. xvi-xvii) the subdermal 
cavities seem to arise as lacunae in the parenchyma. And in 
the external buds of Tethya maza, Selenka (29) believes the 
stbdermal cavities have a similar origin. 
In Spongilla, according to Gétte (6), the subdermal cavities 
and canals are formed as independent lacunae in the parenchyma, 
and the flagellated chambers are formed from groups of cells, 
each group (and chamber) being produced by the budding of 
a single large mesoderm cell. This account of the develop- 
ment of Spongilla is contradicted by Maas (14) who brings 
Spongilla in line with those forms having a rhagon. Maas 
describes in the larva a single central cavity from which the 
chambers arise as diverticula, the central cavity persisting in a 
modified shape as the efferent system of canals. The sub- 
dermal spaces arise as ectodermal invaginations, from which 
the afferent canals are formed as ingrowths. Thus according 
to Maas in the ontogeny of Spongilla, the whole afferent 
system is formed from the ectoderm and the whole efferent 
system from the endoderm. Ganin’s earlier account (7) like- 
wise makes the chambers originate as diverticula from a main 
endodermic cavity. 
In the metamorphosis of a larva, which probably belongs to 
Myxilla, Vosmaer (34) finds the subdermal cavities begin as 
fissures which gradually become wider, and the canals and 
chambers likewise appear as intercellular spaces. 
Finally, in the gemmule development of Esperella and 
Tedania I find that subdermal cavities, both sorts of canals, 
and the flagellated chambers, all arise as independent lacunae 
in the parenchyma. 
Accepting as ancestral the development (¢.e. later develop- 
ment or metamorphosis) of Oscarella and Plakina monolopha, 
the various coenogenetic modifications which appear in other 
sponges may be classified as follows :— 
1. The efferent canal system, instead of arising as a single 
cavity which throws out diverticula, may be formed as so many 
distinct cavities which subsequently unite (Esperella, Tedania, 
Esperia [Maas], Halisarca Dujardinii, Myxilla). 
2. The flagellated chambers, instead of arising as endodermic 
