INTERNAL ANATOJ\lY OF SQUILLA. 
407 
our material tlie entire gland consists of a simple deep 
pocket, somewhat dilated at its blind extremity, which has 
apparently been formed by an involution of tlie hypodermis, 
i.e. the ectodern (Textdig. 1). At a later stage the gland 
consists of two wide sacs which only communicate with each 
other by a narrow tube — the distal or end-sac and the 
Text-fig. 3. 
Transverse section across the end-sac and terminal part of the 
kidney of the gland (in a transverse section of a 14 mm. larva) 
showing the connection (Com.) ])etween the two. Cut. Cuticle. 
Hijp. Hypodermis. Sq. Ep. Squamous epithelium underlying 
hypodermis. End. S. C. End-sac cells. JB. S. Blood-sinus (con- 
tained blood not shown). P. C. Protoplasmic jn’ocesses from 
end-sac cells extending across blood-space to squamous epi- 
thelium. I. M. Invagination of kidney wall in process of 
formation. I. P. Similar invagination of septum sejiarating 
end-sac from kidney. ( X 384.) For other reference letters 
see p. 429. 
proximal sac or gland proper or kiduey, as I shall term it in 
future, which opens to the exterior via the duct (Text-figs. 2 
and 3). During subsequent development each of these 
divisions, but especially the kidney, enlarges greatly, and 
