CONSTITUTION AND DEVELOPMENT OF TERMITES. 47 



At the summit of the mamilla the ectoplasm is reduced to a 

 very thin layer, like a structureless membrane, without trace 

 of striation : this is more fully explained below. 



Passing to the unstriated zone, the ectoplasm of the posterior 

 extremity appears somewhat different from the rest, and forms 

 a layer variable in thickness and aspect, but as a rule not 

 dense. I suppose that this hinder extremity can execute 

 amoeboid movements for the purpose of ingesting the food, 

 which ordinarily consists of more or less bulky particles of 

 wood, sometimes more than half the length of the Protozoon. 



The ectoplasm over the rest of the unstriated zone is dense 

 and homogeneous, forming a thinner and more granular layer 

 when the endoplasra is loaded with food particles. Externally 

 it presents a distinct double outline, which is never distin- 

 guishable in that of the posterior extremity. 



There is no distinct demarcation between the ectoplasm and 

 endoplasm of the unstriated zone ; but the ectoplasm of the 

 striated zone encloses a clear space, which I regard as a 

 lacuna filled with liquid or semi-fluid protoplasm. The ar- 

 rangement of this lacuna will be made clearer by a further 

 description of the mamilla. Its anterior unstriated extremity 

 is separated from the rest by means of a transverse diaphragm, 

 which gives it the form of a skull-cap. This diaphragm is 

 membranous, and possesses a circular median orifice, which is 

 occupied by the rounded and closed apex of a cylindrical tube, 

 situated in the long axis of the striated portion of the mamilla. 

 This tube does not completely occlude the orifice, but is 

 separated from it by an annular space. 



Under the thin membranous ectoplasm of the apical portion, 

 which has been compared to a skull-cap, is a clear space, which 

 I take also to be a lacuna filled with liquid or semi-fluid 

 protoplasm, like the one previously described. And these 

 two lacunae communicate by means of the annular space. 



The walls of the above-mentioned cylindrical tube are also 

 membranous in appearance, and contain a liquid or semi-fluid 

 protoplasm, like the lacuuae. Behind, at the base of the 

 mamilla, this tube widens out considerably ; its walls become 



