468 RICHARD EVANS. 



PLATE 37. 



Fig. 15. — X 350. Complete section of a pupa derived from a larva type 

 D, with consequeutiy very fevr ring-like groups of small cells. Plasmodial 

 aggregations have not yet been formed. It contains cells with vesicular 

 nuclei, in which there is a comparatively large number of yolk bodies {y. 6.). 

 The flagellated cells have disappeared from the upper surface as well as from 

 the lower, and the cells with granular nuclei have nearly formed a complete 

 layer on both surfaces. The remains of the larval cavity (Z. C), not yet 

 obliterated, are seen as small slits near the lower surface, which is a proof 

 that this larva is fixed by the anterior pole. The flagellated cells, especially 

 at the lower surface, present a fan-like arrangement. 



Em. 15 a. — x 1000. Portion of the lower surface of a section from the 

 same larva as that drawn in Fig. 15. It shows the fan-like appearance of 

 the immigrating flagellated cells and the cells with granular nuclei {c.g.n.) 

 passing out between the groups. The nuclei of the flagellated cells which 

 have adhered to the surface of the cell marked c.g.n. have already changed 

 in character. The outline of the cells, however, can be made out. The 

 cells with vesicular nuclei contain several yolk bodies, which, owing to their 

 large size, are easily distinguished from the nuclei of the flagellated cells ; 

 the latter are plastered to the surface of the cell {e.g. n.). There are also 

 a few cells, about half a dozen in number, which belong to the class described 

 as cell groups {g. c), which in this larva are exceedingly few in number, A 

 portion of the larval cavity still remains (Z. C). 



EiG. 15 b. — X 1000. Portion of the lower surface of a section from the 

 same series as Eig. 15. The larger group of flagellated cells, whicli have 

 travelled in, is quite exceptional, as is also the fully developed chamber situated 

 close to it. The presence of this chamber, however, shows that the differ- 

 ence between pupae derived from type D and those derived from type C is 

 only one of degree, the flagellated chambers in the one being much more 

 numerous than in the other. The nucleus of one of the collar-cells is prepar- 

 ing to divide, the chromatin having travelled to the centre of the cell after 

 the nucleus has travelled from the base to the inner end of the cell (cf. Eig. 13, 

 7i.g. c). 



Eig. 16. — X 350. Complete section of pupa slightly older than that drawn 

 in Fig. 15, derived from type D. There are no free cells in the interior, 

 which is filled with " plasmodial aggregations " {pi. a.) in which no cell limit 

 can be detected, though that of the whole group is sharply defined. Spicules 

 {sp.) protrude at the upper surface. 



Fig. 16 «. — X 1000. Portion of the same section as Eig. 16, showing 

 both the upper and lower surfaces. The plasmodial aggregations {pi. a.) are 

 seen depicted on a larger scale. They contain, as a rule, a vesicular 



