No. 3] MORPHOLOGY OF THE STENTORS. 515 



the nuclear membranes. When both moieties had become 

 moniliform they began to draw apart, the anterior remaining 

 in the distal zooid, the posterior lying mainly in the proximal, 

 but about a fifth of its length extending into the distal off- 

 spring. (Fig. 46 g) I have found it generally the case that 

 when the meganucleus has divided somewhat unequally, the 

 longer portion projects beyond the line of constriction into the 

 zooid having the shorter portion. 



An interesting instance of division during coalescence is 

 represented in the series of Fig. 47 a-h. The nucleus had 

 originally 16 nodes. Fusion began at three different points: 

 anterior, middle, and posterior {a), and proceeded slowly, re- 

 quiring more than an hour to reach stage d. The result of 

 the presence of three foci of coalescence was the attraction 

 of material in opposite directions at two points, where conse- 

 quently thin commissures were formed, which soon ruptured, 

 thus breaking the nucleus into three pieces of unequal size 

 (Fig. 47 b, c, d), of which the anterior contained the substance 

 of 8 nodes, the middle of 6 nodes, the posterior of 2 nodes. 

 Each piece soon attained its maximum coalescence, with re- 

 peated change of form {d, e), then the two anterior began to 

 elongate, but the hindmost and smallest remained spherical 

 until nodulation of the others had begun (/, g, h). The an- 

 terior piece, from which 1 2 nodes were formed, was appor- 

 tioned to the distal individual ; the other two, which together 

 gave rise to 8 nodes (making 20 in all from a nucleus previ- 

 ously possessing 16), to the proximal. Thus the posterior 

 zooid started off in life with two separate meganuclei. 



The fourth case, with absence of nuclear division, I have not 

 actually observed, but that it occurs is evident from the con- 

 siderable number of Stentors that possess two distinct mega- 

 nuclei of about equal size.^ 



1 It is not easy to find a satisfactory explanation of the variation in the time at 

 which meganuclear division takes place. Such a variation has not, so far as I 

 know, been observed in other species of Infusoria ; but negative evidence on this 

 point is of little value, considering the small number of recorded observations. 

 The variation in S. cceruleiis is apparently limited to the three periods above 

 stated; I have never seen division during the period of elongation (Fig. 41 c-h). 

 I am inclined to regard the division at time of condensation (Fig. 46 a, b) as the 



