INFUSORIA AND RHIZOPODA. $$ 20, 21, 22. 
32 
CHAPTER IX. 
ORGANS OF REPRODUCTION. 
§ 20. 
The Infusoria propagate by fissuration and gemmation, and never by 
eggs. They have therefore no proper sexual organs. : 
This fissuration occurs longitudinally with some,” transversely with 
others,® and in many of them by both at once.“ Gemmation, on the 
contrary, is very rare. 
s § 21, 
Nearly all the Infusoria and Rhizopdda have in their interior a nicely- 
defined body, a kind of a nucleus, which is quite different, in its compact 
texture, from the parenchyma by which it is surrounded. This nucleus, 
which, in different species, varies much in number and form, performs an 
essential part in the fissuration. For, every time the individual divides 
either longitudinally or transversely, this nucleus, which is usually situated 
in the middle, divides also. So that, in the end, each of the two new individu- 
als has anucleus. When an animal isabout to undergo fissuration, there is 
generally first perceived a change in the nucleus. Thus, in Paramecium, 
Bursaria and Chilodon, the nucleus is sulcated longitudinally or trans- 
versely, or even entirely divided,” before the surface of the body presents. 
any constriction. 
This nucleus, which is of a finely granular aspect and dense structure, re- 
tains perfectly its form when the animal is pressed between two plates of glass,. 
and the other parts are spread out in various ways. By direct light its color 
appears pale yellow. It appears’ to lie very loosely in the parenchyma, 
and sometimes individuals may be observed turning their bodies around it 
as it rests motionless in the centre. From all this, it cannot be supposed 
that this nucleus attaches itself to other parts of the animal, and especially 
to the pulsatory cavities (Vestcule seminales of Ehrenberg). 
§ 22. 
A simple, round, or oval nucleus is found in Euglena, Actinophrys, 
Arcella, Ameba, Bursaria, Paramecium, Glaucoma, Nassula and Chilo- 
don. But there are two which are round, and placed one after the other 
in Amphileptus anser and fasciola, in Trachelius meleagris, and Oxytri- 
cha pellionella. With Stylonychia mytilus, there are four. 
1That which Ehrenberg has arbitrarily taken : 
for eggs is sometimes granules of the parenchyma 
or pigment corpuscles, sometimes bits of food. He 
did not perceive that these bodies want all that which 
is necessary to make up an egg, —such as chorion, 
vitellus, and germinative vesicle and dot. It is on 
this account that he declares that he never has 
observed the hatching of young Infusoria. (Ab- 
handl. d. Berliner Akad. 1835, p. 156.) 
2 Vorticella, Carchesium. 
3 This may be easily observed with Stentor, 
Leucophrys, Lorodes, and Bursaria. 
4 Bursaria, Opalina, Glaucoma, Chilodon, Pa- 
ramacium, Stylonychia and Euplotes. 
5 Vorticella, Carchesium and Epistylis. 
1 Ehrenberg, loc. cit. Taf. XXXVI. fig. vii. 13 
to 19, Taf. XX XIX. fig. ix. 4, 5, 11-13. 
2 Ehrenberg, from a strange fancy, has taker 
this nucleus for a seminal gland. (Abbandl. d, 
Berliner Akad. 1835, p. 163. Also, loc. cit.) 
