32 INFUSORIA AND RHIZOPODA. ^^ 20, 21, 22:. 



CHAPTER IX. 



ORGANS OF REPKODUCTION. 



§ 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.*^^ 



§ 21. 



Nearly all the Infusoria and Rhizopoda 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 a nucleus. When an animal is about to undergo fissuration, there is 

 generally first perceived a change in the nucleus. Thus, in Parai?ioecium, 

 Bursaria and Chilodo?i, 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 (Vesiculce seminales o^ Ehrenberg). '-'^^ 



§ 22. 



A simple, round, or oval nucleus is found in Euglena, Actino'phrys, 

 Arcella, Amcuba, Bursaria, Paramoicium, Glaucoma, Nassula and Chilo- 

 dmi. But there are two which are round, and placed one after the other 

 in AmphUeptus armer and fasciola, in Trachelius meleagris, and Oxytri- 

 cha peiliondla. With Stylomjchia mytilus, there are four. 



1 That which Ehrenbe.rc; has arbitrarily taken 3 This may be easily observed with Stentor, 

 for eggs is sometimes granules of the parenchyma Leucophrijs, Loxoitex, anil Bursaria. 



or pigment corpuscles, sometimes bits of food. He •• liur.taria, Opaliiia, Glaucoma, Chilodon, Pa- 



did not perceive that these bodies wantall that which ramiecium, Stylonychia and Euploten. 



is necessary to make up an egg, — such as chorion, 6 yorliceUa, Carchesium and Epistylis. 



vitellus, and germinative vesicle and dot. It is on ^ Ehrcnberg,\oc. ci\.. Taf. XXXVI. fig. vii. IS 



this account that he declares that he never has to 19, Taf. .XXXIX. fig. ix. 4, 5, 11-13. 



observed the hatching of young Infusoria. (Ab- - Elirenberg, from a strange fancy, has taken 



iandl. d. Berliner Akad. 1835, p. 156.) this nucleus for a seminal gland. (Abhandl. d. 



2 yorticeUa, Carchesium. Berliner Akad. 1835, p. 163. Also, loc. cit.) 



