402 Dr. W. Marshall on new Stliceous Sponges. 
eight*). They are the sponges which persist longest in 
relict-faunas, and can adapt themselves to new forms; thus 
the Caspian Sea still harbours a true Amorphina and three 
other Renierid species of a local genus, Metschnikowia, and 
these four are the only sponges of that great inland seaf. 
The Rentere are almost the only Fibrospongiz that can 
thrive in aquaria. 
These polytropic organisms are able to bear with ease 
diminution of the amount of salt in the water, “as, indeed, 
in general the genus Lendera appears to be especially assigned 
to the lagoons and brackish water’ t. Thus O. Schmidt 
found the brackish bay of Argostoli, in Cephalonia, occu- 
pied by incredible numbers of various Reniere ; the Monac- 
tinellid fauna of Venice consists of more than 57 per cent. 
(four out of seven) of Lenderw, and one of them (. duau- 
rians) also occurs in canals where no other sponges grow, on 
walls immediately below the surtace of the water§. 
The Lubomirskie themselves, although they inhabit fresh 
water, come much nearer to the true Heniere than to the 
Spongille, so near, indeed, that Micluchoj|| at one time did not 
hesitate to unite them with other forms of his true Renierid 
genus Velupsa (polymorpha) as an eleventh variety, batca- 
lensis. In them the trains of spicules are cemented together 
by more strongly developed horny substance than in the 
Spongille, their oscula appear stellate, and gemmules or analo- 
gous structures are wanting. ‘The cause of these differences 
may be, that in Lake Baikal (in which, moreover, a Spon- 
gilla occurs, having probably migrated back, as in the Gulf 
of Finland §]) the conditions of existence do not compel the 
sponges to be annual and to form gemmules; or it may also 
be that, since the Lubomirskie, as true Reniere, were sepa- 
rated from their marine relatives by upheaval of the land, 
time enough has not elapsed for the acquisition of new peculi- 
arities. 
‘There is an important distinction in the fact that these 
sponges are, so to speak, passive inhabitants of the fresh water, 
separated by force from their relatives, while all the other 
* According to Vosmaer, “ Voorloop. Berigt omtrent het onderzoek ” 
&e.. 20 Nov. 1880-20 Feb. 1881, 6 pages, separately paged (? separate 
memoir, or reprint). 
+ There is a memoir by W. Czerniavsky upon the sponges of the Black 
and Caspian seas; but as it is written in Russian it does not exist forme. 
{ Schmidt, Spongien des adriat. Meeres, p. 73. 
§ Schmidt, loc. ct. p. 76. 
| Mém. Acad. Imp. Sci. St. Pétersb. sér. 7, tome xv. no. 3, p. 8 
4} Dybowski, Mém. Acad. Imp. Sci. St. Pétersb. sér. 7, tome XXvil. 
no. 6, p. 66. 
a 
