PLATE XLVIII. 



PAGE 



Fig. 1. Es^wrella lapidiformis, portion of section of embryo ; a., portion of 

 the main mass; c, cap of large, nucleated cells; n., nuclei; m., 

 investing membrane ; x 190, . . . . . lii 



Fig. 2. Esperella murrayi, portion of horizontal section, taken at right angles to 

 the surface; ect., ectosome ; ch., choanosome ; p.a., crack -like j^ore- 

 area, seen in transverse section ; s. , elongated subdermal cavity, 

 seen in transverse section ; i.e., inhalent canal, seen in longitudinal 

 section; e.c, exhalent canal, seen in transverse section; f.c, 

 flagellated chambers, lying in the trabeculse of tissue between the 

 inhalent and exhalent lacunae {I.); d.s., dermal skeleton; /., fibres 

 of the main skeleton ; e, embryo, in the act of escaping through an 

 exhalent canal ; x 13, . . . xxx, xxxix, xlvi, &c. 



Fig. 2a. Portion of the surface of the sponge, showing the crack-like pore-areas, p.a. ; 



the pore-bearing dermal membrane has been removed at p.a'., showing the 



openings of the inhalent canals (i.e.) in the floor of the elongated subdermal 



cavities (s.c.) ; x 2. 

 Fig. 2b. Portion of the dermal membrane from a pore-area ; p., the pores ; /., the bands 



of fibrous (muscular) tissue; »., the nuclei of the epidermic cells; /*'., the 



nuclei of the fibrous cells ; x 180. 

 Fig. 2«. Portion of a section like that represented in Fig. 2, more highly magnified ; 



comprising only the ectosome surrounding an inhalent canal (i.e.); c, darkly 



staining, amffiboid (1) cells, lying in the gelatinous ground-tissue ; t., tricho- 



di'agmata; w., walls of the inhalent canal; s., sigmata, projecting into the 



lumen of the inhalent canal; x 190. 

 Fig. 'M. Portion of section of the choanosome ; f.c, flagellated chambers ; c, mesodermal 



cells; e., epithelial cells lining the canals ; x 190. 



The spicules are printed in blue. 



