4 The American Naturalist. [January, 



newformed duplicate Infusoria multiplied subsequently by- 

 spontaneous division. From one Oxytrachia cut in two, Nuss- 

 baum succeeded in raising ten normal animalcules, which 

 subsequently all encysted. After an unequal division, the 

 parts are both still capable of regeneration, but parts without 

 a nucleus did not survive, which suggests that the formative 

 energy is in some way bound up with the nucleus. But nu- 

 cleate pieces may break down. Thus, all attempts at artifi- 

 cial multiplication of the multinucleate Opalina failed, al- 

 though the division of ActinosphaBrium had been successfully 

 made by Eichhorn as long ago as in the last century. Pelo- 

 myxa palustris has been successfully divided by Greef, and 

 Myastrum radians by Haeckel. 



Gruber (I c, p. 718) describes his experiments with Stentor : 

 " If one divides a Stentor transversely through the middle, 

 and isolates the two parts, one finds on the cut surface of the 

 hind part, after about twelve hours, a complete peristomial field 

 with the large cilia and buccal spiral newly formed. On the 

 other hand, the piece on which the old mouth is situated has 

 elongated itself backwards, and attached itself in the manner 

 peculiar to these Infusoria. If one has made a longitudinal 

 section, so that the peristom is cut in two, then the peristoms 

 both complete themselves and the lateral wounds heal over. 

 I have repeatedly separated, by transection, pieces consider- 

 ably less than half of the original Stentor, and these have also 

 regenerated themselves to complete animals." Gruber, too, 

 observed that artificially divided Infusoria were capable of 

 subsequent spontaneous multiplication. If the section is not 

 very deep, there may arise double monsters ; but here, just as 

 in spontaneous divisions, as long as there remains an organic 

 connecting band, the two parts act as one individual, showing 

 thatthe nervous actions are not restricted to determined 

 paths. Gruber also adds that two divided pieces may be re- 

 united if brought together quickly enough. The observation 

 thus briefly announced is of such extreme interest and impor- 

 tance that the publication of the full details of the experiment 

 will be eagerly awaited. Gruber adds that at present we can- 



