326 REPORT—1850. 
becoming complicated by the development of gemme ; indeed the commence- 
ment of gemmation may be observed before any other change is apparent. 
Meyen* was the first to record the presence of locomotive embryos in the 
freshwater Polyzoa. He observed them in Aleyonella fungosa, but his descrip- 
tion differs in some points from that here given, and he mistakes the ciliated 
sac for the external membrane of an egg containing two embryos. This 
egg, he tells us, becomes ruptured at its anterior extremity and allows the 
embryos gradually to escape. The bodies however here described are of a 
nature totally different from eggs; they are in reality embryos complicated 
by a previous development of gemme, and thus containing a double system 
of digestive and respiratory organs, and destined to undergo an ulterior 
development in all their parts. The little animals originally described by 
Miiller+ as infusorial animalcules, under the name of Leucophra heteroclyta, 
are shown by Meyen to be identical with the locomotive embryos of Aleyo- 
nella fungosa, a fact which corroborates a previously expressed notion of 
Raspail as to the identity of Leucophra heteroclyta and Aleyonella fungosa f. . 
I have now described the three distinct modes of reproduction which may. 
be observed in the freshwater Polyzoa. The colony extends itself by the 
production of gemme, which, after development, remain permanently adhe- 
rent; it establishes new colonies by eggs and free embryos. In Cristatella 
and Lephopus I have also observed the multiplication of a colony by a 
process of self-division. In Cristatella this commences by a constriction 
which takes place generally towards the middle of the colony, and which 
gradually deepens, till at last it divides the entire mass into two separate por- 
tions, which move off in opposite directions. In Lophopus the process is very 
similar; large specimens of this Polyzoon have the endocyst constricted at 
intervals, so as to give to the colony the appearance of a variously-lobed 
body enveloped in the gelatinous-looking ectocyst ; it is at the point of these " 
constrictions that the self-division takes place, separating the entire colony 
into two or more smaller ones. 
It may perhaps be thought that I ought to have enumerated this multipli- 
cation of colonies by a self-division as a fourth form of reproduction ; but as 
in all these cases the division is wholly confined to the ccencecium, the poly- 
pides themselves invariably remaining entire, it is truly referable to the first 
of the modes just enumerated, being really a reproduction by gemme with 
separation of the gemmz in masses. It is analogous to the gemmiparous 
generation in Hydra, and is totally distinct from the true fissiparous genera- 
tion of the lower forms of simple animals. 
ZOOGRAPHICAL OUTLINE. 
Diagnosis of Genera and Species, and Synonomy. 
Genus 1. CristaTeLia, Cuvier (1798). 
Gen. Char.—Ceenecium sacciform, hyaline, with a common flattened dise 
adapted for locomotion. Orifices placed on the surface opposite to the 
dise, and arranged in several concentric marginal series. Lophophore 
crescentic. Ova lenticular, with an annulus and marginal spines. 
Species unica. Cristatella mucedo, Cuvier. 
Characters the same as those of the genus. 
Synonyms. 
1755. Der Kleinere Federbusch-Polyp. R6sel, Insect. Belustig. Supp. p. 559. 
tab. 91. (Original figure.) 
* Loe. cit. + O. F. Miller, Animalcula Infusoria, p. 158. t Raspail, loc. cit. 
