80 W, ARCHER. 



In the body-mass occur several iiucleolated nuclei and con- 

 tractile vacuoles. Encysting sometimes is met with, but no 

 further development has been noticed. The so-called " con- 

 jugation" accompanied with a kind of rhythmical temporary 

 interchange of the plasma is a common phenomenon, inter- 

 preted by Her twig and Lesser as merely the expression of an 

 act of division, inasmuch as so frequently one of the indi- 

 viduals is of the deep reddish-brown of the mature form, the 

 other yellowish or colourless, the latter presumably the 

 younger ; the two individuals presently separating and each 

 "going its way." 



Since Hertwig and Lessor's work, however, Biitschli has 

 published a memoir,^ in which he seems to return to the view 

 that the conjugation has, at least, sometimes, a greater signi- 

 ficance than merely the expression of an act of division. He 

 found (as sometimes happens) three all alike highly coloured 

 individuals conjugated ; afterwards, when separated, these 

 showed a portion of the body-mass broken up into a number 

 (as many as nine) of minute "Amoebae," with nucleus and 

 contractile vacuole. These made their way out from the 

 parent-test, and Biitschli supposed them to be germs of 

 young Arcelte, but was not able to follow out their develop- 

 ment any further. How such amoeboid germs develope tests 

 and become Arcellse is uncertain, and, adds the author, "this 

 would be of great interest, for I can hardly suppress the 

 doubt that such forms as the PseudocJilatnys patella, Clap, 

 et Lachm., and the Arcella patens of the same observers, 

 may not belong to the development-cycle of Arcella vulgaris." 

 This latter view I venture to hold, with Hertwig, as alto- 

 gether unfounded. 



' 0. Biitschli, " Zur Kenntniss der Fortpflanzung dei, Arcella vulgaris" 

 in ' Scbultze's Archiv,' Bd. xii, p. 459, t. xxv. 



{To be continued. 



