Viscosity Changes of Protoplasm 179 



channels. These thin areas, as Camp noted, may become fenestrated; 

 the protoplasm partly retracts and partly solates and becomes incor- 

 porated into the tubes, contributing endoplasm and material to the 

 gel wall. If one followed the fate of tiny terminal channels leading 

 to the pseudopod which is destined to form the center of the advanc- 

 ing sector, it would be noted that this channel without moving for- 

 ward would gradually enlarge until it became the main tube with the 

 thick gel wall. 



The channels in the anterior part of the transition zone through 

 which the endoplasm flows are surrounded by the broad gel sheet 

 and do not have definite walls. In the posterior part where the 

 channels are larger there is a gradual transition into tubes that 

 have more and more definite walls like those on the tubes into which 

 they are continued. Probably all the changes which the transition 

 zone undergoes can be correlated with the building up of the 

 advancing sector and "demand" for endoplasm. Camp has described 

 many of the changes which took place in the broad continuous sheet 

 which I have designated as the transition zone without indicating 

 their relation to the building up of the advancing sector. Camp 

 states (p. 327) that the "Protoplasmic movement or locomotion in a 

 plasmodiuni is so similar to the same phenomenon in the rhizopods 

 that when the correct explanation is found for the one, it will prob- 

 ably hold true in most of its aspects for the other." Although he 

 quotes Mast at some length, he does not apply the principles of 

 ameboid locomotion to the plasmodium. If one applies these prin- 

 ciples, all the visible changes fall into line. 



The broad crescentic anterior end is thick, and it is often difficult 

 to see exactly what happens from moment to moment. The anterior 

 ends are usually more or less lobulated. In some preparations all 

 the migrating plasmolets show marked lobulation, while in others 

 it is almost absent. During the forward flow of the endoplasm, the 

 tip of each lobule expands and extends forward into one or more 

 pseudopodia or protuberances described by Camp. In some prepar- 

 ations the forward flow of the granular endoplasm usually completely 

 fills the rather rapidly expanding pseudopod. In other preparations, 

 the expanding tips often become filled with granule-free hyaloplasm 

 (Figs. 1-4) . Camp suggests that the granules cannot enter because 

 the hyaline pseudopod is too thin. This may apply to some cases, 

 but many of those that I have observed are thick and rounded and 

 have ample thickness for the granules. At the base of such a 

 hyaline cap there is a slightly rounded, bulging layer of granular 



