SPIROSTOMUM AMBIGUUM 



397 



E lid o p 1 a s 111 a ii d Nuclei .-^Tlie eiidoplasni consists of 

 large vacuoles separated by narrow meshes of fairly fluid 

 protoplasm. In the endoplasm lies the long moniliform mega- 

 nucleus. In the living animal its form can be followed quite 

 easily, since its denser structure and greater powers of refrac- 

 tion readily distinguish it from the rest of the protoplasm. 

 Normally it consists of a single unbranched chain, extending 

 in a fairly straight or slightly zigzag manner from the anterior 

 end to the contractile vacuole. The lobes, which vary con- 



TeXT-FIGS. 1 AND 2. 



Ccuval of 



cordj^ctcUle 



vacLooLe 



e^JjopLasm 



Ccuuxl of 

 vcocccoLe. 



vacuoLatext 

 ervcLopUxan. 



enxLopLasni 



^pLcLSnt 



siderably in size, are joined together by commissures which may 

 be either almost as wide as the lobes themselves or very narrow. 

 The lobes vary also in number. The least number I have ever 

 seen in any member of the large variety was ten and the greatest 

 number was fifty. 



In some animals, the nucleus, although it was normal in 

 length, had an unconstricted, vermiform shape and in places 

 was slightly coiled. In all other respects the individuals seemed 

 quite normal and the position of the mouth (see part on Fission) 

 did not point to any very recent or immediately approaching 

 fission. I found, however, by isolating these individuals and 

 keeping them under observation for a number of hours which 

 varied wuth the individual, that lobation eventually did take 

 place and that it was in this case delayed for a much longer 



