394 Dr. W. Marshall on new Siliceous Sponges. 
third point, viz. the production of gemmules, that can be 
regarded as a fundamental criterion of a sponge belonging to 
the group of the Spongillina of Carter, as indeed is done by 
Carter * when he characterizes the group thus :—“ Bearing 
seed-like reproductis e organs called ‘ statoblasts.’”” According 
to this the species of the genus Lubomirskia from Lake 
Baikal would be at once excluded, for, according to Dybow- 
ski’s ¢ positive assertion, they have no gemmules. 
But are these gemmules of the other freshwater sponges 
really so eminently characteristic that they alone are capable 
of demonstrating the relationship of those sponges? or may 
they not make their appearance as new formations sue 
generis in originally different forms—that is to say, in forms 
of different origin? ‘This is open to discussion. 
Besides sexual reproduction an asexual process seems to be 
rather widely diffused among sponges. Leaving out of con- 
sideration the gemmule-formation in freshwater sponges, it 
has been observed in Gumminee (/Zalisarca, F. Ei. Schulze), 
Monactinellide (Rinalda?, Mereschkowsky), ‘Tetractinellidee 
(Tethyade, Deszé, Selenka, Perceval Wright), and very pro- 
bably in Hexactinellide ; at least the young individuals 
observed by Carter { on the lateral tufts of spicules of adult 
Rosselle seem to me to belong to this category of buds, as 
indeed the above-mentioned naturalist himself remarks, “ It 
seems probable, if these [several minute specimens] do not 
originate in ova which have respectively fixed themselves 
there for development, that they arise from pullulation or 
budding.” Iam now even inclined to interpret as buds the 
young forms discovered by me in the body-cavities of a speci- 
men of LHyalonema Steboldi, and previously described as 
embryos §. 
According to Selenka || each bud in Zethya maza consists 
of at least from five hundred to one thousand mesodermic cells, 
and it is his opinion that in the T'ethyadz asexual and sexual 
repro luction are mutually exclusive; in Tetilla radiata trom 
Rio de Janeiro he found during the winter months, from June 
to August, no ova in course of segmentation along with the 
buds. I have myself repeatedly examined Yethye in the 
budding state, both living (at Corfu) and very well preserved, 
and especially a number trom the ‘longa archipelago were of 
* Ann. & Mag. Nat. Hist. February 1881, p. 88. 
+ “Studien uber d. Spong. d. russ. Reichs,” Mém. Acad. St. Pétersb, 
sér. 7, tome xxvii. no. 6, p. 11. 
t{ Ann. & Mag. Nat. Hist. ser. 4, vol. xv. p. 118 (1875). 
§ Zeitschr. f. wiss. Zool. Band xxv. Supp. p. 216. 
|| Zeitschr. f. wiss. Zool. Band xxxiii. p. 473. 
