400 ANN BISHOP 



composed of chromatin, since it stains darkly with the various 

 haematoxyhn and carmine stains and with methyl green. 

 This endosome seems to be homogeneous and is surrounded by 

 a pale area or halo, around which there appears to be a definite 

 membrane. 



In his summary of our knowledge of the multinucleate 

 ciliates Calkins (4) says that ' Balbiani, in his earlier work at 

 least, held that the number of micronuclei is always the same 

 as the macronuclei, or in beaded forms, as many as there are 

 segments of the macronucleus '. He goes on to say that 

 Maupas (18), Gruber, Biitschli, and others disproved this view. 

 They found that the numbers were the same in some ; in 

 other cases, of which Stentor is an example, the micronuclei 

 outnumber the segments of the macronucleus ; whilst in other 

 forms, including Spirostomum ambiguum, the seg- 

 ments of the macronucleus outnumber the micronuclei. I can 

 fully endorse the statement that the micronuclei do not 

 correspond in number to the lobes of the meganucleus, for 

 I have seen individuals in which a number of lobes had no 

 micronuclei near to them, whilst others have two, or in some 

 cases three, four, or five to each lobe. The micronuclei are 

 found opposite to the commissures as well as opposite to the lobes. 



In the majority of individuals which I examined, however, 

 the number of lobes of the meganucleus is greater than the 

 number of micronuclei. In a number of cases there have 

 been nearly twice as many lobes of meganucleus as micronuclei 

 present. On the other hand, quite an appreciable number of 

 individuals have been observed in which the micronuclei were 

 approximately equal in number to the lobes of the meganucleus 

 or slightly exceeded them. In one case where the number of 

 lobes in the meganucleus was only ten, twenty-six micronuclei 

 were present. 



From these observations it seems clear that, subsequent 

 to fission, in the change from a vermiform to moniliform type 

 of ]iucleus, there is no correlation between the number of con- 

 strictions appearing in the meganucleus and the number of 

 micronuclei present in the daughter Spirostomum. 



