2 Frut. 
TRUTOZOA. 
A ciliate Infusorian, infesting the skin of young trout in aquaria, 
residing in tumours of the epidermis, is described by Fouquet (5) as 
Ichthyophthirius multifiliis [sic]. It has a horseshoe-shaped nucleus, a 
nucleolus only in the young state, many contractile vesicles, no vent nor 
mouth, but a mouth-like organ of attachment (degraded moiith). After 
leaving its abode in the skin of the fish, it sinks to the bottom, encysts 
itself, and divides, by repeated segmentations, into a number of small 
individuals, similar to the adult, but more elongate, &c. 
Maupas (7) describes the fixed and locomotory state alternately 
assumed by Podophrya fixa, and by an allied form which he describes as 
var. algirensis, but which is evidently a separate species. The biological 
phenomena are, however, almost identical in both. The fixed condition 
is not ahvays pedunculate, but most commonly so in P. fixa. The change 
from the fixed to the mobile state is introduced by the vdthdrawing of 
the tentacles or suckers, which finally disappear, while vibratile cilia are 
developed over a definite portion of the body, the shape of the body 
being altered from globular to elongate, &c. The animalcules reassume 
the immobile condition on protrusion of the suckers, disappearance of the 
cilia, &c. The whole process may be completed in fifty minutes. Divi- 
sion is also observed in the fixed stage, but before going away, the sepa- 
rating half goes through the metamorphosis characterising the change 
from the fixed into the free stage. Butsciili (2) has re-examined the 
formation of the “ zoospore ” (swarming germ) in P. quadripartita. 
There are always in the normal slate of this species three contractile vesi- 
cles, forming a regular triangle, and a nucleus of inverted conical shape. 
When described otherwise, the presence of the germ has not been ob- 
served. The gemmule is formed as an internal bud ; its appearance is 
preceded by the formation of an orifice, destined to give an exit to the 
zoospore when mature ; during its growth, it encloses a part of the nucleus, 
the shape of which is changed, and the structure whereof, from granular, 
becomes fibrillate ; after the birth of the zoospore, the portion of the 
nucleus enclosed by it and that remaining in the mother-animal resume 
their typical shape and structure ; at birth, the zoospore is provided with 
a girdle and tuft of cilia, three vacuoles, &c. Koch (6) has observed on 
Plumularia setacea two new species, Podophrya pusill a and Ophryodendrum 
pedunculatwm, the last in two shapes, between whicjh a genetic relation 
evidently prevails, but the precise nature of which was not made out. 
Engelmann (4) has shown that the typical, full-grown Opalina ranarum 
is developed from young, found encysted in the intestine of tadpole 
of frogs ; origin unknown. The young Opalina has only a single nucleus, 
which during growth is multiplied by fission, resulting in a large 
number of these bodies. The other chapters of Engelmann’s investiga- 
tions are especially devoted to the relation of the “nucleus” to the con- 
jugation in the Infusoria \ while in the composite (polypoid) Vorticellina, 
division (fission) is the only known method of propagation, a true gem- 
mation (unequal fission) takes place in Vorticella microstoma \ during 
this process a portion of the nucleus is severed and becomes the nucleus of 
the bud (microgonidium) . These freely-swimming small bell-animalcules, 
whether produced by budding or by fission (as in Epistylis), are con- 
