138 
SCHEME OF HOMOLOGOUS PARTS. 
MEDUSA. 
Ectotheque, 
Manubrium, 
Ectoderm* of Manubrium 'j 
confining tbe generative l 
elements (Medusa of Tu- j 
bularidce), 
Generative Elements [in 
walls of Manubrium (Me 
dusa of Tubularidce) ; in 
walls of Radiating canals 
(Medusa of Campanu- 
laridce)~\, t 
Endoderm of Manubrium . 
surrounded by the gene* I 
rative elements (Medusa ( 
of Tubularidce), 
Umbrella, 
Radiating canals, 
Circular canal, 
Marginal tentacles, 
Velum, 
Mouth, 
Oral tentacles, 
SPOROSAC. 
Ectotheque, 
Endotheque + Spadix 
Endotheque, 
Generative Elements, 
0 
Body of Polype. 
Ectoderm of Body. 
Spadix, 
Coecal processes 
from Spadix, 
0 
0 
0 
0 
0 
Endoderm of Body. 
Tentacles (posterior 
tentacles in Tubu- 
lar ia). 
0 
0 
0 
Mouth. 
Oral tentacles (Tubu- 
lar ia). 
Ccenosarc. 
A Statical Barometer, on Father Secchi’s principle, was 
exhibited by Professor Forbes. 
The Following Donations to the Library were announced 
Proceedings of the Royal Society, London. Vol. IX., No. 31. 
8vo . — From the Society. 
The Twenty-fifth Annual Report of the Royal Cornwall Polytechnic 
Society, 1857- 8vo . — From the Society. 
* Professor Huxley’s important demonstration of the composition of the 
proper radiata out of two membranes, must be carefully borne in mind in all 
our attempts to establish relations of homology in this group. 
t It is highly probable that the medusae whenever produced among the 
Tubularidae, will be found to have their generative elements formed between 
the endoderm and ectoderm of the manubrium ; while, on the other hand, in the 
medusae of the Campanularidae and Sertularidae, the generative elements will 
originate in the walls of the radiating canals, here also between endoderm and 
ectoderm. In the former, therefore, the medusae would approach the type of 
Sarsia, in the latter that of Thaumantias, or more exactly that of Eucope, 
Gegenb. Perhaps, however, until a greater number of instances are accumu- 
lated, it would be hardly safe to insist on the validity of this generalization. 
