iNrrsoRiA. 71 



cavity soon becomes formed at its opposite extre- 

 mity*^; at the same time a nucleus and contractile 

 vesicle may be observed in its interior, Ultimately 

 tlie ovate body escapes through a rupture formed 

 in the wall of the cyst, which soon after closes, 

 and after a while a new nucleus is produced in 

 its interior, which in its turn may become trans- 

 formed in the same manner as its predecessor. 



Relations somewhat similar to those which con- 

 nect Vorticella and Aclneta have been affirmed by 

 Haime to exist between Aspidisca (or Trichoda) 

 {fig, 13, d) and Oxytricha (c). 



If these statements be admitted as true, it 

 follows that important modifications will be thereby 

 effected in our views as to what constitutes a 

 " genus " or " species " among the Infusoria; since 

 they would appear to show that ' Acineta^ and 

 Podojjliyra, usually considered to be distinct genera, 

 are rather to be regarded as intermediate or transi- 

 tional forms produced by the metaphormosis of 

 encysted Vorticellce. But the conclusions of Stein 

 have recently been altogether rejected by Lach- 

 niann and others, who assert that in none of his 

 observations did he take sufficient care to isolate 

 the specimens submitted to examination. 



It sometimes happens that two or more Infu- 

 soria cohere together, but in an imperfect manner, 

 a line of demarcation being always observable 



between them {fig. iS^ 9 ^^^ ^)' ^^ ^^^^ union 

 (the object of which has not yet been ascertained) 

 the term "conjugation" is often improperly applied. 

 d. Under the head of true reproduction the 

 following series of changes, recently observed in 

 Paramecium by Balbiani, would seem to be de- 

 serving of mention. Two Paramecicc adhere toge- 



F 4 



