532 



JOHNSON. [ \' o L. V 1 1 1 . 



right. The meganucleus was ah-eady in the noded condition, 

 and as nearly as could be made out in the living animal, was 

 in two pieces, one of ten nodes lying in the proximal zooid, the 

 other of twelve nodes lying for the most part in the distal. A 

 contractile vacuole was present in each zooid. 



The first change observed was the appearance of two new 

 zones (Fig. 6iA, <?.^.,^ a.c}), one for each zooid. That on the 

 posterior zooid {a.s.~) appeared a little before the other, but the 

 evolution of the two went on very nearly pari passu. Three 

 hours later a new mouth had appeared at the lower extremity of 

 each, (<?.,^ o}) and at the same time the meganucleus had under- 

 o-one condensation into three or four masses. Six hours after the 

 appearance of the new zones, o.- had been drawn up into the 

 position of the absent mouth of the posterior zooid (Fig. 6iC), 

 and at nearly the same time o} had taken the place of o. An- 

 other change which had probably been in operation since the 

 finding of the specimen, had by this time become very evident : 

 viz., the forward movement of the whole posterior frontal field 

 and zone to the plane of the anterior. Possibly it would be 

 more accurate to describe the change as a tvithdrawal of the 

 anterior zooid into the posterior. Whichever movement took 

 place, its important result was to bring the two frontal fields 

 to the same level, and therefore the two parts of the double 

 monster into closer union. 



The next observations were made 1 5 hours later, and revealed 

 a great change in the appearance of the monster (Fig. 61 D). 

 It now had one immensely large frontal field composed of the 

 two preexisting frontal fields, and encircled by an adoral zone 

 made up of repeated neoformations arising at two different 

 places on the body. The patchwork character of the zone is 

 clearly marked by the numerous breaks in the series of mem- 

 branellse. The dualism of the specimen is still manifest in 

 the arrangement of stripes in the frontal field in two distinct 

 systems, in the development of two more new zones, and in the 

 two contractile vacuoles {c.v., c.v.^). 



A point of much interest is the conte7nporaneity of the oral 

 renovation, now observed for the second time in this specimen. 

 In both instances the synchronism in the neoformation of oral 



