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FIG. 58. 



Development of Clathrina blanca as seen in sections. 1, larva ; l a -l<*, four stages in the 

 modification and immigration of a ciliated cell into the inner mass ; 2, section of pupa after 

 completion of metamorphosis (first day) ; 3, section of pupa on the second day. The immigra- 

 tion of cells from the dermal epithelium, to form the skeletogenous stratum, is going on actively, 

 the porocytes are aggregated in the centre, and the gelatinous ground substance is making its 

 appearance. 4, section of pupa early on the third day. The gastral cavity, lined by porocytes, 

 and the spicules have appeared. 5, section of pupa towards the end of the fourth day. The 

 gastral cavity is lined by gastral cells, which are commencing to develop collars and flagella, 

 while their nuclei are migrating towards the bases of the cells. The spicules are large ; the 

 position of the future osculum is indicated ; the porocytes are migrating outwards ; and the 

 amoebocytes have changed in appearance, am.c, amoebocytes ; cil.c, ciliated cells ; G.C, 

 gastral cavity ; osc, osculum ; p.c, porocytes ; p.g.c, posterior granular cells ; skel, skeleto- 

 genous stratum ; spic, spicules. 



