CELL INCONSTANCY IN HYDATINA SENTA 463 



and phase of life cycle of the individuals whose glands were 

 studied. The facts, as far as recorded, are given in tables 7, 8, 

 9 and 10. 



With the exception of male-producers, as contrasted with 

 female-producers (table 10), none of the various conditions men- 

 tioned in tables 7 to 10 seem to be associated with deviations in 

 the number of nuclei in the gastric glands. The nmnber of nu- 

 clei deviates from the usual number six in periods of few or man}^ 

 male-producers, in adults of different ages, and in those reared 

 in spring water or in manure solution. And in view of the small 

 number of individuals studied, it is not impossible that the ab- 

 sence of aberrant glands in male-producers is insignificant. The 

 minimum aberrant number is 33.3 per cent below the normal, 

 the maximum 16.6 above the normal. It is also worthy of note 

 that in only one specimen studied were both gastric glands aber- 

 rant, one of them having seven nuclei, the other five. 



DISCUSSION 



In two of the smaller organs of the rotifer Hydatina senta, an 

 organism said to be highly constant in the number of its cells, 

 it is now found that the. number of nuclei varies. In the case 

 of one organ, 4 per cent of those examined contained other 

 numbers of nuclei than those claimed for it ; in the other organ, 

 7.5 per cent were aberrant. In both organs, the highest num- 

 ber found is approximately double the lowest number. In one 

 organ the nuclei are of moderate size, in the other enormous, so 

 that they are readily counted. 



If those who have found the numbers of cells in the organs of 

 this rotifer highly constant have been misled in the case of small 

 organs whose nuclei are easily counted, there is no reason to as- 

 sume that their counts are any more accurate in the case of larger 

 organs where the counting is difficult. If other organs are as 

 variable as the yolk gland and the gastric glands, and if the fac- 

 tors which change the cell number from the 'normal' can or cr- 

 ate in the same direction in all organs, then by rare chance the 

 supposed nine hundred and fifty-nine cells in the whole body 

 might be either six hundred and forty or eleven hundred and 



