158 Miscellaneous. 
liker to submit the Gregorine to fresh observation. The following 
are the conclusions at which he arrives in his last memoir :— 
1. The Gregorine are animals. 
2. The simple Gregorine are decidedly composed of a single cell. 
Their membrane corresponds to the cellular membrane; their con- 
tents are those of acell; the vesicle which it contains represents the 
nucleus; the granulations (sometimes there is only one) of the latter 
are simple or disaggregated nucleoli. These simple Gregorine are 
only met with in Annelides. 
3. The Gregorine with constricted body most probably correspond 
also to a simple cell of a peculiar form. They are met with in in- 
sects and crustacea. 
4. There is no reason for not considering the Gregorine as animals 
which have attained their most perfect state. 
5. The cases of pseudo-navicelle with granular contents and with 
vesicles probably proceed from a transformation of the Gregorine. 
6. The presence of two nuclei or of two cells in the interior of 
certain Gregorine indicates either the commencement of their repro- 
duction or their transformation into pseudo-navicelle.—Zeitschrift 
fiir Wissenschaftliche Zoologie, i. p. 1. 
NYCTOTHERUS, a new genus of PotyGastrRica allied to PLESCONIA. 
By Dr. Lerpy. 
Body ovate, dilated posteriorly, compressed anteriorly, granulated, 
longitudinally lined, with an apparent operculum covering its an- 
terior half, and having a semicircle of cilia just within its margin in- 
feriorly and posteriorly. Centre of the operculated portion furnished 
with a large trapezoidal finely granular areola. Posterior part of the 
body with a short fissure passing inwards and downwards. 
Nyctotherus velox. Body white, ovate, conoidal, anterior margin 
rounded, obtuse ; pesteriorly acute. Posterior margin of the apparent 
operculum passing in a curved line upwards upon the middle of the 
body to within a short distance of the back, and furnished inferiorly 
with a point projecting backwards ; with a line passing down from 
the back about the middle of the operculum to the trapezoidal areola, 
giving the part of the body anterior to this the appearance of a head. 
Trapezoidal areola with curved sides, finely granular. Posterior 
fissure communicating with the exterior, just above the acute termi- 
nation of the body, and passing inwards and downwards, resembles 
an anal aperture. Areole of the interior sarcous mass generally 
minute, one large and round pretty constantly to be observed at the 
inner termination of the posterior fissure. 
Length from 1-254th to 1-180th in.; breadth from 1-320th to 
1-254th in. 
Hab. Commencement of the large intestine of Julus marginatus, 
often found in considerable numbers. 
Remarks. This genus is closely allied to Plesconia, but possesses no 
appendages excepting the semicircle of cilia, just within the edge of 
the apparent operculum. 
The animal swims in water with great ease and grace. After being 
