§23. 



INFUSORIA AND RHIZOPODA. 



83 



It is not rare that a variable number of these round nuclei, arranged in 

 a row, traverse the body in a tortuous manner. This is so in Stentor 

 coeruleus and polymorphus, in Spirostomum avihigmim, and in Tracheliiis 

 moniliger. In many instances the nucleus has the form of an elongated 

 band, which is slightly curved in Vorticella convallaria, Epistylis levcoa, 

 Prorodon niveus and Bursaria truncatella. In Stentor RcBselii, it is 

 spiral, and in Euplotes patella and Trichodina mitra, it is shaped like a 

 horse-shoe. In Loxodes bursaria, it is kidney-form, and encloses in one of 

 its extremities a small corpuscle (nucleolus). 



The round nucleus of Euglena viridis has in its centre a transparent 

 dot. In Chilodon cucullulus, the nucleolus has a similar dot, and thus the 

 nucleus as a whole resembles a cell. 



§ 23. 



These nuclei, which make Infusoria resemble cells, deserve a special 

 attention, since they do not die with the animal. Thus the nucleus of 

 Euglena viridis, which, according to Ekrenberg,^^^ is globular when dying, 

 and surrounded by a kind of cyst, remains unchanged a long time, or even 

 increases in size, having no appearance of a dead body. It may be that 

 the life of this animal, under these circumstances, is not finished, but only 

 assumes another form,<^^ 



1 Loc. cit. p. 110. 



2 Perhaps this nucleus, of which the animal is 

 only a temporary envelope, is ultimately developed 

 into a particular animal. Indeed, perhaps this 

 species, as well as many others, are only the larval 

 etiites of other animals, whose metamorphoses are 

 yet unknown. It may properly be asked, if this 

 nucleus has not, relative to the body containing it, 

 the same signification as have tiie tubulous larvae 

 of Monostomum mutaOile (see below) to the em- 

 bryos they surround. 



That the nucleus contained in Infusoria plays an 

 import.ant part in the propagation of those animal- 

 cules, is supported also by a recent observation of 

 Focke, who witnessed the development of several 

 young individuals in the nucleus of Loxodes bur- 

 saria. See Amtl. Bericht iiber die 22 tr. Versaaml. 

 deutsch. Naturforscher, in Bremen, Abth. ii. p. 

 110. 



