470 „ lilOHARD EVANS. 



PLATE 38. 



Fig. 20. — X 1000. Portion of section of a pupa slightly more advanced 

 than that drawn in Figs. 19 and 19 a, derived from type D. The small flagellated 

 cells have extricated themselves almost completely from the plasmodial aggre- 

 gations, and are arranged in irregular rings {n.fi. c.) round the cavities of the 

 future chambers. The cell limits are beginning to reappear. The future collar- 

 cells, i. e. the former flagellated cells, are in some cases beginning to develop a 

 collar which protrudes into the chamber cavity (C). The subdermal cavity 

 {S. C.) has increased in size considerably, and the cavities in the interior are 

 becoming differentiated into inhalant and exhalant canals. The nucleus marked 

 V. n. on the left side of the figure and the four small nuclei {n.jl. c.) situated 

 close to it present a most interesting case of the nuclei of the flagellated cells 

 acquiring the characters of collar-cell nuclei, before breaking away from the 

 cell with vesicular nudeus. 



Fig. 21. — x 1000. Portion of a section of a still more advanced pupa 

 than that from which Fig. 20 was drawn, also derived from type D. The 

 flagellated chambers are well defined, and the inhalant and exhalant canals 

 are becoming lined with cells possessing granular nuclei, which are gradually 

 flattening out. The cells with vesicular nuclei are situated close to the 

 flagellated chambers in many cases. The collar-cells have almost completely 

 developed collars and flagella, though the latter are difficult to trace. 



Fig. 23. — X 1000. Portion of a section of a slightly more advanced pupa 

 than that represented in Fig. 21, derived from type D. The inhalant and 

 exhalant canals (J. C. and Tl. C.) communicate with the cavity of the chamber 

 {C.) by means of a prosopyle («./?.) and the apopyle (e.p.). The collars are 

 fully developed, and unite together by their margins to form the so-called 

 " membrane of Sollas." 



PLATE 39. 



EiG. 23, — X 1000. Surface view of the marginal membrane of an indivi- 

 dual slightly more advanced than that represented in section in Fig. 15. The 

 individual cells of the membrane are quite separate, and all contain granular 

 nuclei. The flagellated cells, which in some cases are carried away by the 

 cells with granular nuclei, are plastered to the surfaces of the latter, and 

 now exhibit a definite outline. 



Fig. 23 «. — x 1000. A portion of the same preparation slightly nearer the 

 centre than that drawn in Fig. 23, Note how the flagellated cells become 

 attached to both cells with vesicular nuclei and cells with granular nuclei, 

 and that in many cases they are still free. 



Pigs. 24, 24 a, 24 i. — x 1000. Surface views of an individual which had 



