COHN, ON NASSULA ELEGANS. 99 
long since accurately described by Ehrenberg, and in which 
that observer counted twenty-six teeth; and the nucleus con- 
tained in the interior of the body. This nucleus is of an 
elliptical shape, is 1-40’” in length, and has a groove at 
one end, in which is lodged a minute nucleolus. The entire 
mass is surrounded by a closely fitting vesicle, and in struc- 
ture corresponds very exactly with the nucleus formerly 
described by me in Lowodes bursaria. 
Three contractile vacuoles are described by Ehrenberg in 
Nassula elegans, two of which are said to be situated near 
the oral orifice, and the third upon the ‘central gland” or 
nucleus. I have, myself, only noticed two corresponding to 
the first and second thirds of the animal; the occurrence of a 
rosette-form in these vacuoles, as stated by Stein, to take 
place in Nassula ambigua, I have not perceived. 
In the spring of the past year I met with several speci- 
mens of Nassula elegans, in whose interior might be observed 
a large central cavity of an elliptical form and sharply de- 
fined from the rest of the contents of the body. At the 
point where the cavity most nearly approached the external 
wall, the body of the animal presented a flask-shaped depres- 
sion, and an elongated fissure, bounded by parallel walls, 
leading from within to without. In the interior of the cavity 
I observed one or two large spherical bodies 0-001” in 
diameter, but never more than two. These spherical bodies 
slowly entered the fissure through which the cavity commu- 
nicated with the outer world, and in this way escaped into the 
water. Having thus escaped, the spherules appeared mo- 
tionless and colourless, having a granular texture with a 
central nucleus and an excentric contractile vacuole. It 
is a remarkable circumstance, that in these spherical bo- 
dies I observed no trace of the ciliary covering by which 
the movements of the embryos of Lowodes bursaria are 
effected; on the other hand, however, the short, radiating 
capitate filaments figured by Stein and myself in Loxodes, 
were visible. No doubt, therefore, can exist as to the mor- 
phological correspondence of the Nassula-spherules with the 
“swarm-offspring” of Loxvodes, notwithstanding the absence 
in the former of any motion which might possibly be owing 
to the circumstance of their having been prematurely born 
into the cold. I have unfortunately neglected to ascertain 
whether the spherules in Nassula have any relation to the 
nucleus, as asserted by Stein in other cases. The formation 
of the reproductive spherules might even be observed in 
individuals which, having but just undergone division, had 
not attained to half their normal size. It is to be remarked 
