4 Prot, 
rilOTO ZOA. 
newed through the conjugation, which is to be looked upon as a more or 
less complete remodelling or reorganization of the animalcule, resulting 
in the active renewing of the faculty of propagating through fission ; 
this process is analogous to the segmentation of the egg, resulting in the 
one instance in a multicellular organism, in the other in a series of 
generations of unicellular organisms. During the conjugation the ‘^nu- 
cleus’’ is often completely expelled, in the same manner as the “nucleus*' 
of the egg after (or before ?) the fecundation ; the new nucleus is then 
afterwards formed of the products of the division of the “ nucleoli in 
other instances, it is only partially expelled, the remaining portion after- 
wards being united with the new nucleus, formed in the manner described; 
or this body unites itself with the entire old nucleus. The “ nucleoli ” 
are not nucleoli proper ; they are not qualitatively different from the nuclei, 
and their number is independent of that of the nuclei ; the (secondary) 
nuclei are only more strongly developed and modified “ nucleoli ’* (prim- 
ary nuclei) ; these are not wanting (as supposed) in the Vorticellina, and 
will probably be found in all Infusoria. During their division (and that 
of the animal) and after each conjugation, they assume (like the nuclei of 
the Infusoria and the “ germinal vesicles ” of the eggs of higher animals) 
a fibrillate structure (if that is.iiot present before), which disappears when 
the division is at an end. This fibrillation, however, is not a formation 
of spermatozoids, and they do not exercise any visible fecundating power. 
Thus the sexual theory of Balbiani is as utterly rejected as the embry- 
onal theory of Stein, while the unicellularity is upheld in all its force, 
a plurality of nuclei being, according to Blitschli, quite compatible with 
unicellularity. 
According to the remarkable researches of E. van Beneden (8) the 
Dicyemidoi are neither worms nor Protozoa, but occupy an intermediate 
position, being “ Mesozoaf viz., pluricellular animals, consisting of ecto- 
derm and entoderm, but without any mesoderm ; [this the author sup- 
poses to bo present in all Coilenterata, a supposition which still must be 
regarded as doubtful. They therefore must form by themselves one of 
the primary divisions of the animal kingdom, representing a state of 
evolution, which has left no other vestige among known living forms. 
Van Beneden distinguishes 4 genera and 7 species ; — Dicyema typus from 
the spougious renal bodies of Octopus vulgaris ; D. clausiana from 0. 
macropus ; Dicyemella wageneri from Medone moschata ; D. mulleri from 
E. cirrosa ; Dicyemina kollikeriana from Sepia officinalis ; D. schulziana 
from S. hiserialis ; Dicyemopsis macrocephalus from Sepiola rondeleti. 
The body of the Dicyemidoi consists of a single elongate axial or endo- 
dermal cell and a not very large (sometimes specifically definite) number 
of epithelium-like vibratile ectodermal cells ; there are no other cavities, 
no mouth or vent, no muscular fibrils, &c. A definite number of the 
foremost ectodermal cells are differentiated into a sort of head ; other 
ectodermal cells are often distended by accumulation of corpuscles, and 
form wart-like protuberances, which give to the specimens a peculiar 
physiognomy. The embryos are all produced in the axial cell ; they are 
of two kinds, vermiform (filiform) and infusoroid, and each species of 
Dicyemidoi exists in the double shape ; “ nomatogouous ” individuals, 
