54 Vidvcrsitij of Califoriiia Publications in Zoologij [Vol. 20 



sides with their darkly staining- strands drawn out beyond the central 

 core and terminating in a point (pi. 6, fig. 10) with a complete obliter- 

 ation of the core. Some curious modifications of this are sometimes 

 seen in which a considerable amount of the darkly staining material 

 has accumulated at the tip and is thrown out sideways into hornlike 

 processes (pi. 6, fig. 9; pi. 8, fig. 34; fig. C, 6). 



This axial structure extends backward for a short distance from 

 the apex of the cone, tubular in shape or slightly larger posteriorly 

 (pi. 5, figs. 1, 6). Near its base the separate strands, which are 

 usuallj' quite distinct, become enlarged into broad, irregular, darkly 

 staining masses (fig. C) which appear to fray out around their distal 

 margins. These may sometimes be separated (pi. 6, figs. 9, 13) into 

 ropelike and brushlike masses, or an almost continuous band may be 

 formed around the base of the tubular part of the neuromotor appa- 

 ratus (pi. 6, fig. 7). Distally these masses break up into the oblique 

 fibers which have been described above. The two structures seem to 

 be continuous and composed of the same material. They connect the 

 centroblepharoplast with the external motor organs, the flagella, by 

 their intimate association with their basal granules. 



Alveolar Layer : Closely filling the same regions traversed by the 

 oblique fibers is a layer of alveoli (fig. B, alv.; pi. 7, fig. 24). This 

 is continuous in extent with the other ectoplasmic structures, but 

 along the posterior border it may sometimes seem to merge into the 

 larger endoplasmic alveoli which often fill the posterior portion of the 

 body (pi. 5, fig. 6). 



In cross-section the alveoli seem fairly regular (pi. 5, fig. 4), and 

 are placed closely together. In surface view they appear less regular 

 with larger alveoli in the posterior region. In the rounded dividing 

 forms this layer is often very striking, the alevoli having the appear- 

 ance of clear globules much larger than those usually present in the 

 normal vegetative forms (pi. 7, fig. 24; pi. 12, fig. 76), possibly as a 

 result of pressure. The intra-alveolar spaces are traversed by 

 branches from the oblique fibers (pi. 6, fig. 9) and by the basal 

 fibrils of the flagella, the basal granules lying in the zone immedi- 

 ately beneath the alveoli, which is also occupied by the major portion 

 of the oblique fibers (pi. 5, fig. 4). The zone lying between the 

 alveolar layer and the surface is also traversed by these basal fibrils 

 which give to that region a striated appearance (pi. 5, fig. 5). Optical 

 sections from, the posterior border of the ectoplasm in a dividing 

 trichonymph (pi. 12, fig. 80) .show the ba^al granules lying close 



